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41650 Publications

Global Polynomial Level Sets for Numerical Differential Geometry of Smooth Closed Surfaces

Thekke Veettil, Sachin K.; Zavalani, G.; Hernandez Acosta, U.; Sbalzarini, Ivo F.; Hecht, M.

Abstract

We present a computational scheme that derives a global polynomial level set parametrisation for smooth closed surfaces from a regular
surface-point set and prove its uniqueness. This enables us to approximate a broad class of smooth surfaces by affine algebraic varieties. From such a
global polynomial level set parametrisation, differential-geometric quantities like mean and Gauss curvature can be efficiently and accurately computed. Even 4th-order terms such as the Laplacian of mean curvature are approximates with high precision. The accuracy performance results in a gain of computational efficiency, significantly reducing the number of surface points required compared to classic alternatives that rely on surface meshes or embedding grids. We mathematically derive and empirically demonstrate the strengths and the limitations of the present approach, suggesting it to be applicable to a large number of computational tasks in numerical differential geometry.

Keywords: Numerical differential geometry; surface approximation; mean curvature; Gauss curvature; level set

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  • ARXIV: 2212.11536 is previous version of this (Id 36064) publication

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Permalink: https://www.hzdr.de/publications/Publ-36064


Application Experiences on a GPU-Accelerated Arm-based HPC Testbed

Elwasif, W.; Godoy, W.; Hagerty, N.; Harris, J. A.; Hernandez, O.; Joo, B.; Kent, P.; Lebrun-Grandie, D.; Maccarthy, E.; Melesse Vergara, V. G.; Messer, B.; Miller, R.; Oral, S.; Bastrakov, S.; Bussmann, M.; Debus, A.; Steiniger, K.; Stephan, J.; Widera, R.; Bryngelson, S. H.; Le Berre, H.; Radhakrishnan, A.; Young, J.; Chandrasekaran, S.; Ciorba, F.; Simsek, O.; Clark, K.; Spiga, F.; Hammond, J.; Stone, J. E.; Hardy, D.; Keller, S.; Piccinali, J.-G.; Trott, C.

Abstract

This paper assesses and reports the experience of ten teams working to port,validate, and benchmark several High Performance Computing applications on a novel GPU-accelerated Arm testbed system. The testbed consists of eight NVIDIA Arm HPC Developer Kit systems built by GIGABYTE, each one equipped with a server-class Arm CPU from Ampere Computing and A100 data center GPU from NVIDIA Corp. The systems are connected together using Infiniband high-bandwidth low-latency interconnect. The selected applications and mini-apps are written using several programming languages and use multiple accelerator-based programming models for GPUs such as CUDA, OpenACC, and OpenMP offloading. Working on application porting requires a robust and easy-to-access programming environment, including a variety of compilers and optimized scientific libraries. The goal of this work is to evaluate platform readiness and assess the effort required from developers to deploy well-established scientific workloads on current and future generation Arm-based GPU-accelerated HPC systems. The reported case studies demonstrate that the current level of maturity and diversity of software and tools is already adequate for large-scale production deployments.

Keywords: ARM; HPC; NVIDIA; GPU; CUDA; OpenACC; OpenMP; alpaka; PIConGPU

  • Open Access Logo Contribution to WWW
    Preprint: https://arxiv.org/pdf/2209.09731.pdf
    DOI: 10.48550/arXiv.2209.09731
  • Open Access Logo Contribution to proceedings
    HPC Asia 2023 Workshop: International Conference on High Performance Computing in Asia-Pacific Region Workshops, 27.02.-02.03.2023, Singapore, Republic of Singapore
    The Proceedings of International Conference on High Performance Computing in Asia-Pacific Region Workshops, New York, NY, USA: The Association for Computing Machinery, 978-1-4503-9989-0, 35-49
    DOI: 10.1145/3581576.3581621
    Cited 1 times in Scopus

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Permalink: https://www.hzdr.de/publications/Publ-36063


Coupled processes across a 10-year-old clayrock/concrete interface: results of a combined X-ray CT and PET transport experiment

Bernard, E.; Kulenkampff, J.; Jenni, A.; Mäder, U.

Abstract

Interfaces between clay and cementitious materials are studied in the context of deep disposal of radioactive waste. Contrasting porewater chemistries lead to transport and chemical reactions that modify the pore network and affect transport. Research efforts were directed towards mineralogical and physical characterisation of interface regions (e.g. Mäder et al. 2017, Swiss J. Geosci. 110, 307) but little evidence exists on direct observations of transport behaviour across complex skins. We aim at providing evidence on how mineralogical-physical changes at such an interface affect transport of water and solutes, and linking mineralogical-physical characterisation.
A core was recovered at the Mont Terri rock laboratory (CI Experiment), containing a physically preserved interface between Opalinus Clay and Portland cement (PC) concrete reacted for 10 years. A long-term transport experiment was set up by injecting a synthetic claystone pore water into the core on the clay side, and forcing advection/diffusion across the interface and out of the cement side.
Before injection, the core was tomographed by X-ray CT; the clay part showed pre-existing bedding-parallel weak jointing and the PC concrete contains aggregates and gas pores. Figure 1 (left) shows the core skeleton during the infiltration, i.e. only the aggregates in the concrete and the dense Opalinus Clay.
A series of X-ray CT scans over time showed the change in porosity, while PET (positron emission tomography) directly images the mobile phase in 3D, and its penetration as a function of time (Kulenkampff et al., 2016, Solid Earth, 7, 1217). The sample was monitored frequently by high resolution X-ray CT during the first 4 months. 124I was used as PET tracer in the infiltrating synthetic claystone pore water, and the chosen dose allowed for continuous PET scanning during two weeks. Figure 1 (right) shows the flow observed by PET superimposed to the skeleton of the core. PET captured some preferential flow across claystone along some remaining joints, a large spreading of the tracer plume at the clay/cement interface, and some preferential flow across the PC.
The mineralogical and chemical changes coupled to the time-resolved 3D X-ray CT and PET scans (imaging both the stationary and the mobile phase) provide detailed information of coupled processes in complex porous media, e. g. how the dissolution of hydroxide cement phases and the precipitation of carbonates are influenced by advection/diffusion and vice versa.
Partial funding from the European Union's (Euratom) Horizon 2020 Programme under grant agreement 662147 – Cebama is acknowleged, and contributions by Nagra and the Mont Terri Consortium (CI Experiment) to Uni Bern.

Keywords: cement-clay interface; X-ray CT; PET; transport

  • Lecture (Conference)
    Clay Conference, 13.-16.06.2022, Nancy, France

Permalink: https://www.hzdr.de/publications/Publ-36062


Exploiting Heterogeneous Architectures: Applications and Lessons Learned

Stephan, J.

Abstract

In this talk we show the benefits of using performance portability layers such as alpaka in real-world HPC applications. Using PIConGPU and the CMS Patatrack experiment as examples we demonstrate the minimal porting effort achieved by using alpaka when encountering new and previously unknown hardware architectures.

Keywords: PIConGPU; alpaka; cupla; heterogeneous architectures; heterogeneous systems; heterogeneous programming; C++; performance portability; software portability; HPC

  • Open Access Logo Lecture (others)
    Thirteenth INFN International School on: "Architectures, tools and methodologies for developing efficient large scale scientific computing applications" (ESC 2022), 03.-08.10.2022, Bertinoro, Italia

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Permalink: https://www.hzdr.de/publications/Publ-36061


Introduction to Software Portability Among Heterogeneous Architectures

Stephan, J.

Abstract

In this talk we first introduce the concept of heterogeneous computing systems and then show the difficulties that lie in programming them. We present the different workload patterns that are suitable for different hardware types. In the end propose the alpaka kernel abstraction library as a possible solution to these challenges.

Keywords: heterogeneous systems; heterogeneous programming; software portability; performance portability; alpaka; C++; heterogeneous architectures; parallel programming; SYCL; Kokkos; RAJA; cupla; LLAMA; vikunja

  • Open Access Logo Lecture (others)
    Thirteenth INFN International School on: "Architectures, tools and methodologies for developing efficient large scale scientific computing applications" (ESC 2022), 03.-08.10.2022, Bertinoro, Italia

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Permalink: https://www.hzdr.de/publications/Publ-36060


Data Publication: Ab initio path integral Monte Carlo simulations of hydrogen snapshots at warm dense matter conditions

Böhme, M.; Dornheim, T.; Moldabekov, Z.; Vorberger, J.
Project Manager: Dornheim, Tobias; ResearchGroup: Moldabekov, Zhandos; RelatedPerson: Vorberger, Jan

Abstract

This is the archived datasets used for the publication in the article: Ab initio path integral Monte Carlo simulations of hydrogen snapshots at warm dense matter conditions. The dataset also contains the data-analysis python scripts.

Keywords: Path-Integral Monte-Carlo; Warm Dense Hydrogen; Many-body physics

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Permalink: https://www.hzdr.de/publications/Publ-36059


The alpaka SYCL back-end

Stephan, J.

Abstract

In this talk the kernel abstraction library alpaka is briefly introduced. Afterwards the technical details of the alpaka SYCL back-end are presented.

Keywords: alpaka; SYCL; heterogeneous programming; HPC; parallel programming

  • Open Access Logo Lecture (others) (Online presentation)
    Patatrack Students Meeting, 18.10.2022, Genf, Schweiz

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Permalink: https://www.hzdr.de/publications/Publ-36058


QED.jl - Strong-field particle physics code

Hernandez Acosta, U.; Steiniger, K.; Jungnickel, T.; Bussmann, M.

Abstract

We present a novel approach for an event generator inherently using exact QED descriptions to predict the results of high-energy electron-photon scattering experiments that can be performed at modern X-ray free-electron laser facilities. Our event generator makes use of the fact, that the classical nonlinearity parameter barely approaches unity in high-frequency regimes accessible at these facilities, while this parameter range is outside of the application window of existing QED-PIC codes. This constraint on the parameter range allows for an approximation which is capable of taking the finite bandwidth of the X-ray laser into account in the description of the interaction.
We investigate the application of the new first-principle method to the generation of events in energy-driven electromagnetic cascades, which complements the studies on intensity-driven cascades at optical laser experiments.

  • Poster
    International Conference on Quantum Systems in Extreme Conditions (QSEC2022), 14.-18.11.2022, Bingen am Rhein, Germany

Permalink: https://www.hzdr.de/publications/Publ-36057


First steps in QED cascades - the onset stage

Hernandez Acosta, U.

Abstract

While the high frequency of modern x-ray free-electron lasers has the benefit of requiring less energy of a seed electron for triggering the development of a QED cascade, the non-linearity parameter obeys a_0 < 1, in contrast to high-intensity optical lasers. Accordingly, we analyse the phenomenon of multi-photon effects in trident pair production in pulsed x-ray laser fields at such values of a_0. The impact of the energy spectrum and its temporal structure and the coherence of the laser field on the emergent particle distribution at the onset of further cascading is discussed. Besides the evolution of mean multiplicities in the course of an energy-powered cascade, we seek characteristic fluctuation patterns.

Keywords: Strong-field QED; Pair production; Electromagnetic cascades; Trident process

  • Invited lecture (Conferences)
    QED Laser Plasmas (qlasp22), 26.-30.09.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36055


Event generation in Julia

Hernandez Acosta, U.

Abstract

The accurate modelling of laser-matter interaction is a very challenging task. Especially, the generation of scattering events to mimic statistical particle distributions seen in experiments have demanding requirements on the computational methods and implementations. With this talk, we introduce the complicated structure of strong-field QED and formulate the fundamental building blocks for Monte-Carlo event generation using this theory, where a key feature is the dynamical coupling of the laser field to the scattering processes. This type of coupling can not be addressed with state-of-the-art event generators used to model processes from the standard model of particle physics. Therefore, we introduce a new implementation of e Monte-Carlo event generator, written in the Julia programming language. Furthermore, we introduce some key language features of Julia, which may come in handy for implementations of future event generators in general, where especially the capabilities of distributed computing will be highlighted.

Keywords: Laser-Matter interaction; Event generation; Julia programming language

  • Invited lecture (Conferences) (Online presentation)
    HSF Physics Generator WG meeting, 07.07.2022, virtuell, virtuell

Permalink: https://www.hzdr.de/publications/Publ-36054


Microstructuring YbRh₂Si₂ for resistance and noise measurements down to ultra-low temperatures

Steppke, A.; Hamann, S.; König, M.; Mackenzie, A. P.; Kliemt, K.; Krellner, C.; Kopp, M.; Lonsky, M.; Müller, J.; Levitin, L. V.; Saunders, J.; Brando, M.

Abstract

The discovery of superconductivity in the quantum critical Kondo-lattice system YbRh₂Si₂ at an
extremely low temperature of 2 mK has inspired efforts to perform high-resolution electrical
resistivity measurements down to this temperature range in highly conductive materials. Here we
show that control over the sample geometry by microstructuring using focused-ion-beam
techniques allows to reach ultra-low temperatures and increase signal-to-noise ratios (SNRs)
tenfold, without adverse effects to sample quality. In five experiments we show four-terminal
sensing resistance and magnetoresistance measurements which exhibit sharp phase transitions at
the Néel temperature, and Shubnikov–de-Haas (SdH) oscillations between 13 T and 18 T where we
identified a new SdH frequency of 0.39 kT. The increased SNR allowed resistance fluctuation
(noise) spectroscopy that would not be possible for bulk crystals, and confirmed intrinsic 1/ f -type
fluctuations. Under controlled strain, two thin microstructured samples exhibited a large increase
of T̀N from 67 mK up to 188 mK while still showing clear signatures of the phase transition and
SdH oscillations. Superconducting quantum interference device-based thermal noise spectroscopy
measurements in a nuclear demagnetization refrigerator down to 0.95 mK, show a sharp
superconducting transition at T̀c = 1.2 mK. These experiments demonstrate microstructuring as a
powerful tool to investigate the resistance and the noise spectrum of highly conductive correlated
metals over wide temperature ranges.

Permalink: https://www.hzdr.de/publications/Publ-36051


Unconventional Spin State Driven Spontaneous Magnetization in a Praseodymium Iron Antimonide

Pabst, F.; Palazzese Di Basilio, S.; Seewald, F.; Yamamoto, S.; Gorbunov, D.; Chattopadhyay, S.; Herrmannsdörfer, T.; Ritter, C.; Finzel, K.; Doert, T.; Klauss, H.-H.; Wosnitza, J.; Ruck, M.

Abstract

Consolidating a microscopic understanding of magnetic properties is crucial for a rational design of magnetic materials with tailored characteristics. The interplay of 3d and 4f magnetism in rare-earth transition metal antimonides is an ideal platform to search for such complex behavior. Here the synthesis, crystal growth, structure, and complex magnetic properties are reported of the new compound Pr3Fe3Sb7 as studied by magnetization and electrical transport measurements in static and pulsed magnetic fields up to 56 T, powder neutron diffraction, and Mößbauer spectroscopy. On cooling without external magnetic field, Pr3Fe3Sb shows spontaneous magnetization, indicating a symmetry breaking without a compensating domain structure. The Fe substructure exhibits noncollinear ferromagnetic order below the Curie temperature TC ≈ 380 K. Two spin orientations exist, which approximately align along the Fe–Fe bond directions, one parallel to the ab plane and a second one with the moments canting away from the c axis. The Pr substructure orders below 40 K, leading to a spin-reorientation transition (SRT) of the iron substructure. In low fields, the Fe and Pr magnetic moments order antiparallel to each other, which gives rise to a magnetization antiparallel to the external field. At 1.4 K, the magnetization approaches saturation above 40 T. The compound exhibits metallic resistivity along the c axis, with a small anomaly at the SRT.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-36050


Interparticle Charge-Transport-Enhanced Electrochemiluminescence of Quantum-Dot Aerogels

Gao, X.; Jiang, G.; Gao, C.; Prudnikau, A.; Hübner, R.; Zhan, J.; Zou, G.; Eychmüller, A.; Cai, B.

Abstract

Electrochemiluminescence (ECL) represents a widely explored technique to generate light, in which the emission intensity relies critically on the charge-transfer reactions between electrogenerated radicals. Two types of charge-transfer mechanisms have been postulated for ECL generation, but the manipulation and effective probing of these routes remain a fundamental challenge. Here, we demonstrate the design of quantum dot (QD) aerogels as novel ECL luminophores via a versatile water-induced gelation strategy. The strong electronic coupling between adjacent QDs enables efficient charge transport within the aerogel network, leading to the generation of highly efficient ECL based on the selectively improved interparticle chargetransfer route. This mechanism is further verified by designing CdSe-CdTe mixed QD aerogels, where the two mechanistic routes are clearly decoupled for ECL generation. We anticipate our work will advance the fundamental understanding of ECL and prove useful for designing next-generation QD-based devices.

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Permalink: https://www.hzdr.de/publications/Publ-36048


Plastic instabilities in epitaxial NiMnGa Heusler films

Fareed, A.; Kar, S.; Fähler, S.; Maass, R.

Abstract

Magnetic shape memory alloys are known to undergo stress- and temperature-driven phase changes. Here we study the specific case of a NiMnGa Heusler alloy that has an austenitic phase at room temperature. Upon cooling or the application of mechanical pressure, the austenite can transform into martensite, allowing for large reversible strain cycling and making such alloys to promising actuating materials. In order to shed more light on the mechanical switching behavior and possible dissipative processes, we probe the nano-scale plasticity of 0.5 and 2 µm thick epitaxial NiMnGa films with nanoindentation. A distinct pop-in signature is seen as the first departure from Hertzian elastic contact mechanics at small film thicknesses. This pop-in behavior persists across four orders of loading rates and over a broad temperature regime from 40°C to -30°C, which encompasses the transformation temperature to martensite. The statistics of the incipient plastic events are well described by a Weibull distribution. Atomic force microscopy reveals surface signatures around indents that indicate residual martensite, which is further confirmed with transmission electron microscopy imaging of the structure underneath indents. Instead of the expected modulated martensite (14M, 10M) that forms during a temperature-driven phase change, regions underneath indents contain non-modulated (NM) martensite. NM martensite exhibits a higher spontaneous strain and often forms at lower temperatures and higher strains. Therefore, it is concluded that the pop-in signature during nanoindentation originates from an athermal martensitic transformation, where the confinement effects result in huge and complex deformation inducing a partly irreversible transition to NM martensite.

Keywords: Magnetic Shape Memory Alloys; Nanoindentation

  • Lecture (Conference)
    Nanobrücken 2022: Nanomechanical Testing Conference, 08.-10.06.2022, Prague, Czech Republik

Permalink: https://www.hzdr.de/publications/Publ-36047


What is the speed limit of martensitic transformations?

Fähler, S.; Schwabe, S.; Lünser, K.; Schmidt, D.; Nielsch, K.; Gaal, P.

Abstract

Structural martensitic transformations enable various applications, which range from high stroke actuation and sensing to energy efficient magnetocaloric refrigeration and thermomagnetic energy harvesting. All these emerging applications benefit from a fast transformation, but up to now the speed limit of martensitic transformations has not been explored. Here, we demonstrate that a martensite to austenite transformation can be completed in under ten nanoseconds. We heat an epitaxial Ni-Mn-Ga film with a laser pulse and use synchrotron diffraction to probe the influence of initial sample temperature and overheating on transformation rate and ratio. We demonstrate that an increase of thermal energy drives this transformation faster. Though the observed speed limit of 2.5 x 1027 (Js)-1 per unit cell leaves plenty of room for a further acceleration of applications, our analysis reveals that the practical limit will be the energy required for switching. Our experiments unveil that martensitic transformations obey similar speed limits as in microelectronics, which are expressed by the Margolus–Levitin theorem.
[1] S. Schwabe, K. Lünser, D. Schmidt, K. Nielsch, P. Gaal and S. Fähler, https://arxiv.org/abs/2202.12581

Keywords: Martensitic Transformations; Shape Memory Alloys

  • Invited lecture (Conferences)
    MSE2022, 27.-30.09.2022, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36046


Disentangling nanotwinned microstructures in Ni-Mn-based Heusler alloys from first-principles

Gruner, M. E.; Miroshkina, O. N.; Fähler, S.; Baigutlin, D.; Sokolovskiy, V. V.; Buchelnikov, V. D.

Abstract

Depending on composition and chemical order, Ni-Mn-based Heusler alloys exhibit interesting functional properties, which render them useful for magnetic shape memory applications or as magnetocaloric materials. This is linked to the presence of hierarchically twinned modulated structures in martensite, which can be interpreted as adaptive, self-organized arrangement of [110]-aligned nanotwins consisting of non-modulated tetragonal building blocks as was shown previously for the paradigmatic case of stoichiometric Ni2MnGa [1]. A band-Jahn-Teller-type reconstruction of the Fermi surface which in particular softens the [110] transversal acoustic phonons leads to a downhill transformation path from cubic austenite to nanotwinned martensite [2]. The twin interfaces are subject to competing repulsive and attractive interactions related to the frustrated antiferromagnetic coupling between neighboring Mn atoms [3].
Based on recent first-principles calculations in the framework of density functional theory, the present contribution explores the signatures of the interdependence of magnetism, chemical order and nanotwinning in Ni-Mn-based Heusler systems beyond Ni-Mn-Ga and their relevance for the functional properties. Particular emphasis will be made on off-stoichiometric compositions suitable for magnetocaloric purposes.

Keywords: Magnetic Shape Memory Alloys; Martensite; Twinning; First Principle Calculations

  • Poster
    MSE 2022, 27.-30.09.2022, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36045


In situ stability study of WAlSiN based selective absorber under heating and cooling cycles in vacuum up to 800°C

Lungwitz, F.; Niranjan, K.; Munnik, F.; Hübner, R.; Garcia Valenzuela, A.; Escobar Galindo, R.; Krause, M.; Barshilia, H.

Abstract

In situ measurements using RBS, ERD, and SE are less explored in characterizing solar absorber materials at high temperatures [1, 2]. In the present work, we report the W/WAlSiN/SiON/SiOO2 based spectrally selective solar absorber coating with excellent optical, compositional and structural properties at high temperatures [3, 4]. We have carried out in situ Rutherford backscattering spectrometry, elastic recoil detection and spectroscopic ellipsometry measurements at three different temperatures at 450°C, 650°C, and 800°C. An optical model describing perfectly the reflectance and ellipsometric data was developed. Further, the microstructural properties of the solar absorber coating are evaluated using cross-sectional transmission electron microscopy before and after annealing. Our data obtained before and after the heating experiments demonstrate excellent compositional, optical and structural stability of the coatings under the applied conditions. Furthermore, in situ ellipsometry showed the conservation of the optical properties of the W/WAlSiN/SiON/SiOO2 based spectrally selective solar absorber up to 800 °C, which is crucial for high-temperature applications.
[1] Ramón Escobar Galindo, Matthias Krause, K. Niranjan and Harish Barshilia, in Sustainable Material Solutions for Solar Energy Technologies (ed. Mariana Fraga, Delaina Amos, Savas Sonmezoglu, Velumani Subramaniam, Elsevier, 2021).
[2] Lungwitz, F. et al. Transparent conductive tantalum doped tin oxide as selectively solar-transmitting coating for high temperature solar thermal applications, Solar Energy Mater. Solar Cells 196, 84-93, doi:10.1016/j.solmat.2019.03.012 (2019).
[3] K. Niranjan, A. Soum-Glaude, A. Carling-Plaza, S. Bysakh, S. John, H.C. Barshilia, Extremely high temperature stable nanometric scale multilayer spectrally selective absorber coating: Emissivity measurements at elevated temperatures and a comprehensive study on ageing mechanism, Solar Energy Mater. Sol. Cells 221 (2021) 110905, doi:10.1016/j.solmat.2020.110905.
[4] K. Niranjan, A.C. Plaza, T. Grifo, M. Bordas, A. Soum-Glaude, H.C. Barshilia, Performance evaluation and durability studies of W/WAlSiN/SiON/SiOO2 based spectrally selective solar absorber coating for high-temperature applications: A comprehensive study on thermal and solar accelerated ageing, Solar Energy 227 (2021) 457–467, doi:10.1016/j.solener.2021.09.026.

Keywords: Concentrated solar power; high-temperature solar-selective coatings; nanolaminates; in situ analysis; ion beam analysis; STEM-EDXS imaging

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  • Poster
    PSE 2022 - 18th International Conference on Plasma Surface Engineering, 12.-15.09.2022, Erfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36044


WAlSiN-based solar selective coating stability-study under heating and cooling cycles in vacuum up to 800 °C using in situ Rutherford backscattering spectrometry and spectroscopic ellipsometry

Niranjan, K.; Krause, M.; Lungwitz, F.; Munnik, F.; Hübner, R.; Pemmasani, S. P.; Escobar Galindo, R.; Barshilia, H. C.

Abstract

In situ Rutherford Backscattering Spectrometry (RBS) and Spectroscopic Ellipsometry (SE) were applied to study the compositional and optical stability of a WAlSiN-based solar-selective coating (SSC) at high temperatures in vacuum. The samples were exposed to heating-cooling cycles between quasi room temperature and stepwise-increased high temperatures of 450 °C, 650 °C, and 800 °C, respectively. In situ RBS revealed full compositional stability of the SSC during thermal cycling. In situ SE indicated full conservation of the optical response at 450 °C and 650 °C, and minimal changes at 800 °C. The analysis of the ex situ optical reflectance spectra after the complete thermal cycling gave an unchanged solar absorptance of 0.94 and a slightly higher calculated thermal emittance at 800 °C of 0.16 compared to 0.15 after deposition. Cross-sectional element distribution analysis performed in scanning transmission electron microscopy mode confirmed the conservation of the SSC’s microstructure after the heating – cooling cycles. The study demonstrates compositional, optical, and structural stability of the WAlSiN-based solar-selective coating at temperatures targeted for the next generation of concentrated solar power plants.

Keywords: Concentrated solar power; high-temperature solar-selective coatings; nanolaminates; in situ analysis; ion beam analysis; STEM-EDXS imaging

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-36043


A convolutional neural network with self-attention for fully automated metabolic tumor volume delineation of head and neck cancer in [18F]FDG PET/CT

Nikulin, P.; Zschaeck, S.; Maus, J.; Cegla, P.; Lombardo, E.; Furth, C.; Kaźmierska, J.; Rogasch, J.; Holzgreve, A.; Albert, N. L.; Ferentinos, K.; Strouthos, I.; Hajiyianni, M.; Marschner, S. N.; Belka, C.; Landry, G.; Cholewinski, W.; Kotzerke, J.; Hofheinz, F.; van den Hoff, J.

Abstract

Purpose: PET-derived metabolic tumor volume (MTV) and total lesion glycolysis of the primary tumor are known to be prognostic of clinical outcome in head and neck cancer (HNC). Including evaluation of lymph node metastases can further increase the prognostic value of PET but accurate manual delineation and classification of all lesions is time-consuming and prone to inter-observer variability. Our goal, therefore, was development and evaluation of an automated tool for MTV delineation/classification of primary tumor and lymph node metastases in PET/CT investigations of HNC patients.

Methods: Automated lesion delineation was performed with a residual 3D U-Net convolutional neural network (CNN) incorporating a multi-head self-attention block. 698 [18F]FDG PET/CT scans from 3 different sites and 5 public databases were used for network training and testing. An external dataset of 181 [18F]FDG PET/CT scans from 2 additional sites was employed to assess the generalizability of the network. In these data, primary tumor and metastases were interactively delineated and labeled by two experienced physicians. Performance of the trained network models was assessed by 5-fold cross-validation in the main dataset and by pooling results from the 5 developed models in the external dataset. The Dice similarity coefficient (DSC) for individual delineation tasks and the primary tumor/metastasis classification accuracy were used as evaluation metrics. Additionally, a survival analysis using univariate Cox regression was performed comparing achieved group separation for manual and automated delineation, respectively.

Results: In the cross-validation experiment, delineation of all malignant lesions with the trained U-Net models achieves DSC of 0.885, 0.805, and 0.870 for primary tumor, LN metastases, and the union of both, respectively. In external testing, the DSC reaches 0.850, 0.724, and 0.823 for primary tumor, LN metastases, and the union of both, respectively. The voxel classification accuracy was 98.0% and 97.9% in cross-validation and external data, respectively. Univariate Cox analysis in the cross-validation and the external testing reveals that manually and automatically derived total MTVs are both highly prognostic with respect to overall survival, yielding essentially identical hazard ratios (HR) (HRman = 1.9; p < 0.001 vs. HRcnn = 1.8; p < 0.001 in cross-validation and HRman = 1.8; p = 0.011 vs. HRcnn = 1.9; p = 0.004 in external testing).

Conclusion: To the best of our knowledge, this work presents the first CNN model for successful MTV delineation and lesion classification in HNC. In the vast majority of patients, the network performs satisfactory delineation and classification of primary tumor and lymph node metastases and only rarely requires more than minimal manual correction. It is thus able to massively facilitate study data evaluation in large patient groups and also does have clear potential for supervised clinical application.

Keywords: FDG PET; metabolic tumor volume; MTV; head and neck cancer; HNC; convolutional neural network

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-36042


Comparison between mechanisms and microstructures of α − γ, γ − ϵ and α − ϵ − α phase transitions in iron

Freville, R.; Dewaele, A.; Bruzy, N.; Svitlyk, V.; Garbarino, G.

Abstract

The α↔ϵ, α→γ and γ→ϵ transformations have been characterised in diamond anvil cells under hydrostatic compression conditions. In situ x-ray diffraction of single or oligo-crystals and ex situ SEM-EBSD measurements have been analyzed with multi-grain techniques. The mechanisms of α ↔ ϵ transitions are martensitic, following Burgers paths whiwh requires a high plastic activity. A memory effect of the reversion exists in the vast majority of the sample: the starting orientation of α-Fe single crystal is recovered. Small grains of α-Fe exhibit a new orientation compatible with Burgers path, possibly associated to twinning in ϵ-Fe. Close to the α − γ − ϵ-Fe triple point (8.7
GPa, 750 K), the α → γ transformation undergoes via diffusion and recrystallization of γ-Fe, and γ → ϵ transformation is martensitic but involves no plasticity. As a result, the microstuctures in ϵ-Fe produced by a direct α → ϵ transformation and by α → γ → ϵ transitions path are very different.

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Permalink: https://www.hzdr.de/publications/Publ-36041


A convolutional neural network for automated delineation and classification of metabolic tumor volume in head and neck cancer

Nikulin, P.; Hofheinz, F.; Maus, J.; Cegła, P.; Furth, C.; Kaźmierska, J.; Rogasch, J.; Hajiyianni, M.; Kotzerke, J.; Zschaeck, S.; van den Hoff, J.

Abstract

Deep Learning based approaches for automated analysis of tomographic image data are drawing ever increasing attention in Radiology and Nuclear Medicine. With the advent of the new generation of PET scanners with massively enlarged axial field of view (“total body PET”) the importance of integrating such approaches into clinical workflows will further increase. In the present study we report on our application of a convolutional neural network (CNN) for automated survival analysis in head and neck cancer (HNC): PET parameters such as metabolic tumor volume (MTV), total lesion glycolysis, and asphericity of the primary tumor are known to be prognostic of clinical outcome in HNC patients. Additionally including evaluation of lymph node metastases further increases the prognostic value of PET. However, accurate manual delineation and classification of all lesions is time consuming and incompatible with clinical routine. Our goal, therefore, was development and evaluation of an automated tool for MTV delineation/classification of primary tumor and lymph node metastases in HNC in PET.

Automated delineation of the HNC cancer lesions was per- formed with a residual 3D U-Net convolutional neural network (CNN). 698 FDG PET/CT scans from 3 different sites and 4 public databases were used for network training and testing. In these data, primary tumor and metastases were manually delineated (with assistance of semi-automatic tools) and accordingly labeled by an experienced physician. Performance of the trained network models was assessed by 5-fold cross validation using the Dice similarity coefficient for individual delineation tasks.

Additionally, survival analysis using univariate Cox regression was performed. Delineation of all malignant lesions with the trained U-Net model achieves a Dice coefficient of 0.866 when not dis-
criminating between primary tumor and lymph nodes. Treating primary tumor and lymph node metastases as distinct classes yields Dice coefficients of 0.835 and 0.757 for the respective delin-
eations. The univariate Cox analysis reveals that, both, manually as well as automatically derived total MTVs are highly prognostic with similar hazard ratios (HR) with respect to overall survival
(HR=1.8; P<0.001 and HR=1.7; P<0.001, respectively). To the best of our knowledge, our work represents the first CNN model for successful MTV delineation and lesion classification in HNC. The network quickly performs usually satisfactory delineation and classification of primary tumor and lymph node metastases in HNC using FDG-PET data alone with only minimal sporadic manual corrections required. It is able to massively facilitate study data evaluation in large patient groups and also does have clear potential for clinical application.

Involved research facilities

  • PET-Center
  • Poster
    9th Conference on PET/MR and SPECT/MR & Total-Body PET Workshop, 28.05.-01.06.2022, Isola d'Elba, Italia

Permalink: https://www.hzdr.de/publications/Publ-36040


Experimental and Theoretical Analyses of Adiabatic Two-phase Flows in Horizontal Feed Pipes

Döß, A.

Abstract

The majority of technical separation processes for fluid mixtures utilize the principle of rectification. If a two-phase mixture is fed into the column, possibly undesirable flow morphologies or severe droplet carry-over may occur, which detrimentally affect separation efficiency and equipment integrity. Currently, the two-phase flow behavior in feed pipes is hardly predicable and mostly based on empirical or heuristic methods, which do not properly account for a broad range of possible fluid properties and plant dimensions. As a consequence, costly safety margins are applied. Feed pipes to separation columns are often characterized by horizontal inlet nozzles, small length-to-diameter ratios and complex routing, involving elbows or bends. The pipe lengths are too short to enable the two-phase flow to fully develop, which thus, enters the column with unknown flow morphology. Since developing flows have rarely been studied, today’s engineering practice relies on existing predictive methods for fully developed two-phase flows. Graphical methods can hardly represent gradual transitions between flow regimes. Analytical models provide only simplified flow representations of the two-phase flow that have not yet been qualified for developing pipe flow. In this work, a comprehensive experimental database of horizontal water-air flows in two test sections with nominal pipe diameters of D = 50 mm and D = 200 mm and feed pipe lengths in the range 10 < L/D < 75 was established. This way, the data cover developing pipe flows with entrance lengths typical for two-phase feeds of separation columns and more developed flows that are comparable with the extensively studied reference system water-air. A particular focus was put on the effect of pipe bends on the flow morphology up- and downstream. The flow morphology was captured using imaging wire-mesh sensors. A 4D fuzzy algorithm was applied to objectively identify the flow two-phase morphologies. Based on their fuzzy representation, the flow morphologies were classified and a novel 2D visualization technique is proposed to discuss the flow development along the feed pipes. Undesired flow morphologies (intermittent flow and entrainment) during the operation of two-phase feeds are hardly predictable by conventional design tools. The inception of intermittent flows was analyzed using the experimental data. Consequently, the inception criteria based on the required liquid levels for fully developed intermittent flows were adapted for short entrance lengths. The characteristic dynamics of flow morphologies that are known to cause the onset of entrainment were analyzed. Based on wave frequencies, a predictive criterion for the susceptibility of wavy flows for the onset of entrainment is introduced and applied to straight feed pipes and horizontal 90° bends. Among the dozens available, 66 reduced-order models for the prediction of the void fraction were tested for straight feed pipes and horizontal 90° pipe bends. Thereof, the ones most suitable for variable operating conditions and pipe geometries were identified and adapted. Complementary 3D simulations were performed to verify the applicability of numerical codes (VoF, AIAD) for flows with free interfaces. The flow morphologies were successfully reproduced at macroscopic scale, however, the simulation results rank behind reduced-order models considering their quantitative predicting capabilities.

Keywords: Distillation; Two-phase feed; Flow morphology; Horizontal two-phase flow

Involved research facilities

  • TOPFLOW Facility
  • Doctoral thesis
    TU Dresden, 2022
    PURL: https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-827786

Permalink: https://www.hzdr.de/publications/Publ-36039


Structural stability of transparent conductive oxide tantalum doped tin oxide during high-temperature treatment

Krause, M.; Hoppe, M.; Mendez, A.; Munnik, F.; Rodriguez Garcia, J.; Lungwitz, F.; Gemming, S.; Rafaja, D.; Escobar-Galindo, R.

Abstract

The transparent conductive tantalum doped tin oxide is a potential candidate for applications in concentrated solar power technology, dye-sensitized solar cells and dynamic random access memories [1], [2], [3]. In all these fields, high-temperature stability in air is mandatory to preserve its functionality. In this work we demonstrate the compositional and structural in-air-stability of SnO2:Ta thin films at 650 °C and 800 °C for 12 hours. While the element composition and optical spectra were unchanged and the X-ray diffractograms revealed the conservation of a single-phase rutile-type crystal structure, some strong Raman lines of SnO2:Ta underwent substantial changes upon tempering. Quantum ab initio calculations of pristine and Ta-doped SnO2 with systematically varied point defects indicated that preferentially Sn vacancies and excess O atoms are responsible for these strong and unexpected Raman signatures. These defects are partially healed during high-temperature exposure, but that does not affect the functionality of SnO2:Ta as transparent conductor under these harsh conditions. This study provides a comprehensive understanding of crystal and defect structure of Ta-doped SnO2 prior to and after high temperature treatment in air for the first time and encourages its application in different fields where high-T stability, transparency and conductivity are required.
[1] F. Lungwitz et al., Transparent conductive tantalum doped tin oxide as selectively solar-transmitting coating for high temperature solar thermal applications, Solar Energy Mater. Solar Cells 199, 84 (2019), doi: 10.1016/j.solmat.2019.03.012
[2] R. Ramarajan, et al. Large-area spray deposited Ta-doped SnO2 thin film electrode for DSSC application, Solar Energy 211, 547-559 (2020), doi:10.1016/j.solener.2020.09.042.
[3] C. J. Cho, et al. Ta-Doped SnO2 as a reduction-resistant oxide electrode for DRAM capacitors, Journal of Materials Chemistry C 5, 9405-9411 (2017), doi:10.1039/c7tc03467a
Financial support by the EU, grant No. 645725, project FRIENDS2, is gratefully acknowledged.

Keywords: high-temperature materials; in-air stability; transparent conductive oxide; Ta-doped tin oxide; Raman signatures; point defects

Involved research facilities

Related publications

  • Lecture (Conference)
    PSE 2022 - 18th International Conference on Plasma Surface Engineering, 12.-15.09.2022, Erfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36038


A convolutional neural network for automated delineation and classification of metabolic tumor volume in head and neck cancer in FDG-PET/CT

Nikulin, P.; Hofheinz, F.; Maus, J.; Cegła, P.; Furth, C.; Kaźmierska, J.; Rogasch, J.; Kotzerke, J.; Zschaeck, S.; van den Hoff, J.

Abstract

Aim: Image derived PET parameters such as metabolic tumor volume (MTV), total lesion glycolysis, and tumor asphericity of the primary tumor have been shown to be prognostic of clinical outcome of patients with head and neck cancer (HNC). Evaluation of lymph node metastases in addition to the primary tumor further increases the prognostic value of PET. Such analysis requires, however, accurate delineation and classification of all lesions which is very time-consuming when performed manually. The goal of this study is development of an automated tool for MTV delineation of primary tumor and lymph node metastases in HNC in PET/CT.

Methods: Automated delineation of the HNC cancer lesions was performed with a residual 3D U-Net convolutional neural network (CNN). 698 FDG PET/CT scans from 3 different sites and 4 public databases were used for network training (N=558) and testing (N=140). In these data, primary tumor and metastases were manually delineated and accordingly labeled by an experienced physician. This manual delineation served as the ground truth for network training. Performance of the trained network model was assessed in the test data using the Dice similarity coefficient for primary tumor, metastases, and the union of all lesions, respectively.

Results: The derived U-Net model is capable of accurate delineation of malignant lesions achieving a Dice coefficient of 0.847 for indiscriminative segmentation. Treating primary tumor and lymph node metastases as distinct classes yields Dice coefficients of 0.840 and 0.714 for the respective delineations.

Conclusions: In this work, we present the first CNN model for MTV delineation and classification in HNC. The developed network model allows to quickly perform satisfactory delineation of (and discrimination between) primary tumor and lymph node metastases in HNC with only minimal manual corrections possibly required. It thus is able to improve and to accelerate study data evaluation in quantitative PET and does also have potential for clinical application.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    NuklearMedizin 2022, 27.-30.04.2022, Leipzig, Deutschland
  • Contribution to proceedings
    NuklearMedizin 2022, 27.-30.04.2022, Leipzig, Deutschland
    A convolutional neural network for automated delineation and classification of metabolic tumor volume in head and neck cancer in FDG-PET/CT: Thieme
    DOI: 10.1055/s-0042-1745945

Permalink: https://www.hzdr.de/publications/Publ-36037


Advantages of Using Triboscopic Imaging: Case Studies on Carbon Coatings in Non-Lubricated Friction Conditions

Lorenz, L.; Makowski, S.; Weihnacht, V.; Krause, M.; Lasagni, A. F.

Abstract

Triboscopy focuses on the analysis of the temporal evolution of a tribological system, combining local and time-resolved information, most commonly the evolution of friction. In this work, this technique is applied on measurements, which were carried out with a custom-built ultrahigh vacuum tribometer in ball-on-disc configuration. Based on these experiments, an extended classification to distinguish different triboscopic features is suggested, depending on the persistence in both track position and time: UNIFORM, GLOBAL, LOCAL, and SPORADIC. Further, a filter technique for quantifying triboscopic data regarding this classification is introduced. The new and improved triboscopic techniques are applied to various dry friction measurements of hydrogen-free carbon coatings under varying humidity and pressure. The resulting specific triboscopic features are correlated to wear phenomena, such as counter body coating abrasion, inhomogeneities in the wear track, non-uniform track wear, stick-slip and debris in the contact area, demonstrating the increased analysis and monitoring capabilities when compared to conventional friction curves and wear track images.

Keywords: DLC; ta-C; a-C; friction; wear

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Permalink: https://www.hzdr.de/publications/Publ-36035


Low-Friction of ta-C Coatings Paired with Brass and Other Materials under Vacuum and Atmospheric Conditions

Härtwig, F.; Lorenz, L.; Makowski, S.; Krause, M.; Habenicht, C.; Lasagni, A. F.

Abstract

Vacuum environments provide challenging conditions for tribological systems. MoS2 is one of the materials commonly known to provide low friction for both ambient and vacuum conditions. However, it also exhibits poor wear resistance and low ability to withstand higher contact pressures. In search of wear-resistant alternatives, superhard hydrogen-free tetrahedral amorphous carbon coatings (ta-C) are explored in this study. Although known to have excellent friction and wear properties in ambient atmospheres, their vacuum performance is limited when self-paired and with steel. In this study, the influence of the paired material on the friction behavior of ta-C is studied using counterbodies made from brass, bronze, copper, silicon carbide, and aluminum oxide, as well as from steel and ta-C coatings as reference materials. Brass was found to be the most promising counterbody material and was further tested in direct comparison to steel, as well as in long-term performance experiments. It was shown that the brass/ta-C friction pair exhibits low friction (µ < 0.1) and high wear in the short term, irrespective of ambient pressure, whereas in the long term, the friction coefficient increases due to a change in the wear mechanism. Al2O3 was identified as another promising sliding partner against ta-C, with a higher friction coefficient than that of brass (µ = 0.3), but considerably lower wear. All other pairings exhibited high friction, high wear, or both.

Keywords: diamond-like coatings; wear; tribology; carbon; films

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Permalink: https://www.hzdr.de/publications/Publ-36034


Phase Transformation Induced by High Pressure Torsion in the High-Entropy Alloy CrMnFeCoNi

Chulist, R.; Pukenas, A.; Chekhonin, P.; Hohenwarter, A.; Pippan, R.; Schell, N.; Skrotzki, W.

Abstract

The forward and reverse phase transformation from face-centered cubic (fcc) to hexagonal
close-packed (hcp) in the equiatomic high-entropy alloy (HEA) CrMnFeCoNi has been investigated
with diffraction of high-energy synchrotron radiation. The forward transformation has been induced
by high pressure torsion at room and liquid nitrogen temperature by applying different hydrostatic
pressures and large shear strains. The volume fraction of hcp phase has been determined by Rietveld
analysis after pressure release and heating-up to room temperature as a function of hydrostatic
pressure. It increases with pressure and decreasing temperature. Depending on temperature, a
certain pressure is necessary to induce the phase transformation. In addition, the onset pressure
depends on hydrostaticity; it is lowered by shear stresses. The reverse transformation evolves over
a long period of time at ambient conditions due to the destabilization of the hcp phase. The effect
of the phase transformation on the microstructure and texture development and corresponding
microhardness of the HEA at room temperature is demonstrated. The phase transformation leads
to an inhomogeneous microstructure, weakening of the shear texture, and a surprising hardness
anomaly. Reasons for the hardness anomaly are discussed in detail.

Keywords: high-entropy alloy; high-entropy alloy; high pressure torsion; microstructure; texture; phase transformation; strength

Permalink: https://www.hzdr.de/publications/Publ-36033


Generating synthetic shadowgrams with an in-situ plugin in PIConGPU

Carstens, F.-O.; Steiniger, K.; Pausch, R.; Schöbel, S.; Chang, Y.-Y.; Irman, A.; Schramm, U.; Debus, A.

Abstract

Few-cycle shadowgraphy is a valuable diagnostic for laser-plasma accelerators for obtaining insight into the $\mu$m- and fs-scale relativistic plasma dynamics. To enhance the understanding of experimental shadowgrams, we developed a synthetic shadowgram diagnostic within the fully relativistic particle-in-cell code PIConGPU.
In the shadowgraphy diagnostic, the probe laser is propagated through the plasma using PIConGPU, and then extracted and propagated onto a virtual CCD using an in-situ plugin for PIConGPU based on Fourier optics. The in-situ approach circumvents performance limitations of a post-processing workflow, like storing and loading large output files that result from large-scale laser-plasma simulations.
This poster presents the in-situ plugin and first synthetic shadowgrams from laser wakefield accelerator simulations that are generated by the plugin.

Keywords: Shadowgraphy; Synthetic Diagnostics; In-Situ Plugin; PIConGPU; Laser-Electron Acceleration

  • Poster
    8. Annual MT Meeting, 26.-27.09.2022, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36032


Curvilinear magnetism: from fundamentals to applications

Makarov, D.

Abstract

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics, superconductivity and magnetism [1,2]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films and nanowires [2,3]. In this talk, we will address fundamentals of curvature-induced effects in magnetism and review current application scenarios. In particular, we will demonstrate that curvature allows tailoring fundamental anisotropic and chiral magnetic interactions [4] and enables fundamentally new non-local chiral symmetry breaking effect [5]. Application potential of geometrically curved magnetic architectures is currently being explored as mechanically reshapeable magnetic field sensors for automotive applications, memory, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive electronics relying on thin films [6,7] as well as printed magnetic composites [8,9].

[1] P. Gentile et al., Electronic materials with nanoscale curved geometries. Nature Electronics (Review) 5, 551 (2022).
[2] D. Makarov et al., New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures. Advanced Materials (Review) 34, 2101758 (2022).
[3] D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications (Springer, Zurich, 2022).
[4] O. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Physical Review Letters 123, 077201 (2019).
[5] D. D. Sheka et al., Nonlocal chiral symmetry breaking in curvilinear magnetic shells. Communications Physics 3, 128 (2020).
[6] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[7] G. S. Canon Bermudez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[8] M. Ha et al., Printable and Stretchable Giant Magnetoresistive Sensors for Highly Compliant and Skin-Conformal Electronics. Advanced Materials 33, 2005521 (2021).
[9] R. Xu et al., Self-healable printed magnetic field sensors using alternating magnetic fields. Nature Communications 13, 6587 (2022).

Keywords: curvature effects in magnetism; curvilinear magnetism; printed electronics; human-machine interfaces

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  • Lecture (others)
    Seminar at the University of Kiel, 25.01.2023, Kiel, Germany

Permalink: https://www.hzdr.de/publications/Publ-36031


Pattering data from NPVE software for Helium Ion Microscopy (HIM) irradiation data

Hlawacek, G.; Fowley, C.; Kuria, J.
Project Member: Fowley, Ciaran; Project Member: Kurian, Jinu; Project Leader: Doudin, Bernard

Abstract

Pattering data from NPVE software for Helium Ion Microscopy (HIM) irradiation data

Keywords: focused ion beam; helium ion microscopy; nanopatterning; magnetic

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Permalink: https://www.hzdr.de/publications/Publ-36030


Fungal bioleaching of metals from industrial wastes

Chakankar, M. V.

Abstract

Industrial wastes and wastewaters are important secondary sources for many metals. Recovering these metals from such waste streams helps in resource recycling and reduce the environmental burden. Microbial technology offers an economical alternative to traditional metal recovery. Several bacterial and fungal species are reported for metal bioleaching from different industrial wastes. Use of fungi in bioleaching process offers a variety of advantages. The present study provides an overview of fundamental mechanisms of fungal bioleaching and methods used for the same. The case study of two different industrial wastes is also provided.

  • Invited lecture (Conferences) (Online presentation)
    Fungal Diversity and its novel applications, 09.04.2022, Pune, India

Permalink: https://www.hzdr.de/publications/Publ-36029


Metal recovery by bioionflotation using biosurfactants

Chakankar, M. V.; Pollmann, K.; Rudolph, M.

Abstract

Metal recovery by bioionflotation using biosurfactants

  • Lecture (others) (Online presentation)
    UGC STRIDE Lecture Series- Advances in Life Science Research, 10.02.2022, Kolhapur, India

Permalink: https://www.hzdr.de/publications/Publ-36028


Curvilinear micromagnetism: from fundamentals to applications

Makarov, D.

Abstract

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics, superconductivity and magnetism [1,2]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films and nanowires [2,3]. In this talk, we will address fundamentals of curvature-induced effects in magnetism and discuss realizations of curved low-dimensional architectures and their characterization, which among others resulted in the experimental confirmation of exchange-driven chiral effects [4]. Geometrically curved architectures can support a new chiral symmetry breaking effect: it is essentially non-local and manifests itself even in static spin textures living in curvilinear magnetic nanoshells [5]. The field of curvilinear magnetism was extended towards curvilinear antiferromagnets, offering a novel material science platform for antiferromagnetic spinorbitronics. It was demonstrated that intrinsically achiral 1D curvilinear antiferromagnets behave as a chiral helimagnet with geometrically tunable DMI, orientation of the Neel vector and the helimagnetic phase transition [6]. Application potential of geometrically curved magnetic thin films is currently being explored as mechanically reshapeable magnetic field sensors for automotive applications, memory, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive electronics [7,8].

References:

[1] P. Gentile et al., Electronic materials with nanoscale curved geometries, Nature Electronics (Review) 5, 551 (2022).
[2] D. Makarov et al., New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures, Advanced Materials (Review) 34, 2101758 (2022).
[3] D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications (Springer, Zurich, 2022). https://link.springer.com/book/10.1007/978-3-031-09086-8
[4] O. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism, Physical Review Letters 123, 077201 (2019).
[5] D. Sheka et al., Nonlocal chiral symmetry breaking in curvilinear magnetic shells, Communications Physics 3, 128 (2020).
[6] O. Pylypovskyi et al., Curvilinear One-Dimensional Antiferromagnets, Nano Letters 20, 8157 (2020).
[7] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time, Nature Communications 10, 4405 (2019).
[8] G. S. Canon Bermudez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics, Nature Electronics 1, 589 (2018).

Keywords: curvature effects in magnetism; curvilinear magnetism

Involved research facilities

Related publications

  • Invited lecture (Conferences) (Online presentation)
    8th Quantum Oxide Research Online Meeting (QUOROM-8), 16.02.2023, London, UK

Permalink: https://www.hzdr.de/publications/Publ-36027


Geometrically curved, skin-conformal and self-healable magnetoelectronics

Makarov, D.

Abstract

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics, superconductivity and magnetism [1,2,3]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films and nanowires [3]. In this talk, we will address fundamentals of curvature-induced effects and discuss experimental realisations of geometrically curved low-dimensional architectures and their characterization, which among others resulted in the experimental confirmation of the exchange-driven chiral effects [4]. Geometrically curved magnetic thin films are interesting not only fundamentally. They are the key component of mechanically flexible magnetic field sensors. We will briefly outline activities on shapeable magnetoelectronics [5,6], which includes flexible, stretchable and printable magnetic field sensors for the realisation of human-machine interfaces [7,8], interactive electronics for virtual [9] and augmented [10] reality applications and soft robotics [11] to mention just a few. Very recently, self-healable magnetic field sensors for interactive printed electronics were reported [12]. The presence of the geometrical curvature in a magnetic thin film influences pinning of magnetic domain walls and in this respect it affects the sensitivity of mechanically flexible magnetic field sensors. This is an intimate link between the fundamental topic of curvilinear magnetism and application-oriented activities on shapeable magnetoelectronics. This link will be discussed in the presentation as well.

References
1. P. Gentile et al., Electronic materials with nanoscale curved geometries. Nature Electronics (Review) 5, 551 (2022).
2. D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications. (Springer, Zurich (2022)). https://link.springer.com/book/10.1007/978-3-031-09086-8
3. D. Makarov et al., New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures. Advanced Materials (Review) 34, 2101758 (2022).
4. O. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Physical Review Letters 123, 077201 (2019).
5. D. Makarov et al., Shapeable Magnetoelectronics. Appl. Phys. Rev. 3, 011101 (2016).
6. G. S. Canon Bermudez et al., Magnetosensitive e-skins for interactive devices. Advanced Functional Materials (Review) 31, 2007788 (2021).
7. P. Makushko et al., Flexible Magnetoreceptor with Tunable Intrinsic Logic for On-Skin Skin Touchless Human-Machine Interfaces. Adv. Funct. Mater. 31, 2101089 (2021).
8. J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
9. G. S. Canon Bermudez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
10. G. S. Canon Bermudez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
11. M. Ha et al., Reconfigurable Magnetic Origami Actuators with On-Board Sensing for Guided Assembly. Advanced Materials 33, 2008751 (2021).
12. R. Xu et al., Self-healable printed magnetic field sensors using alternating magnetic fields. Nature Communications 13, 6587 (2022).

Keywords: curvature effects in magnetism; flexible electronics; printed electronics; human-machine interfaces

Involved research facilities

Related publications

  • Invited lecture (Conferences)
    8th International Conference on Superconductivity and Magnetism (ICSM2023), 04.-11.05.2023, Fethiye-Oludeniz, Turkey

Permalink: https://www.hzdr.de/publications/Publ-36026


Curvilinear magnetism: fundamentals and applications

Makarov, D.

Abstract

In this tutorial, we will review recent activities in the field of curvilinear magnetism. In particular, fundamental aspects on controling anisotropy and chiral responses via geometrical curvature will be discussed. Furthermore, activities on the realization and application scenarios of flexible, stretchable and printed magnetic field sensors will be presented.

Keywords: curvature effects in magnetism; curvilinear magnetism; printed electronics; human-machine interfaces; flexible magnetoelectronics

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Related publications

  • Invited lecture (Conferences)
    IEEE Advances in Magnetics conference (AIM2023), 15.-18.01.2023, Moena, Italy

Permalink: https://www.hzdr.de/publications/Publ-36025


Small Molecule Radiotracers for PET Imaging of PD-L1 with Copper-64

Krutzek, F.; Donat, C.; Ullrich, M.; Kopka, K.; Stadlbauer, S.

Abstract

The programmed cell death ligand (PD-L1) is expressed on a number of different tumor entities and inhibits the immune response through binding to PD-1 on T-cells. Immune checkpoint inhibitors (ICI) prevent this blockade and thus can reactivate an immune response. However, only about 30% of the patients respond to an ICI monotherapy. Therefore, clinicians are in need for a non-invasive PET/SPECT radioligand for patient stratification and therapy monitoring.

Based on the structures of non-peptidic PD-L1 inhibitors, six different radiotracers were synthesized and radiolabelled with [64Cu]Cu2+ (HZDR, 30 MeV TR-FLEX cyclotron). Binding affinities were determined on PC3 cells stably overexpressing hPD-L1. For in vivo studies, qualitative PET/CT imaging experiments (nanoSCAN PET/CT, Mediso) were performed in NMRI-FoxN1-nude mice bearing PC3-hPD-L1 and mock xenograted tumors.

Two PD-L1 inhibitors were modified with strongly water-soluble acid groups, hydrophilic linker units and a NODAGA-chelator resulting in six different radioligands. The log(D) values of the copper-64 labelled radiotracers were between –3.17 and –4.15 and binding affinities ranged between 80.5 and 533 nM. Depending on the number and the pattern of sulfonate and phosphonate groups, in vivo experiments showed drastically different pharmacokinetic profiles. The radiotracer with one sulfonate and phosphonate group and the most hydrophobic linker exhibited a short circulation time, renal clearance, good tumor uptake (SUVmax = 3.5) and a distinct contrast between the hPD-L1 and the mock tumor.

In conclusion one PD-L1 radiotracer showed a promising pharmacokinetic profile, which is currently further modified to improve the binding affinity and tumor uptake.

Involved research facilities

  • PET-Center
  • Lecture (Conference) (Online presentation)
    The 8th International Electronic Conference on Medicinal Chemistry, 01.-30.11.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36024


Synthesis and Biological Evaluation of Chelator-Based Small Molecule PET-Radiotracers for Imaging of PD-L1

Krutzek, F.; Donat, C.; Ullrich, M.; Kopka, K.; Stadlbauer, S.

Abstract

Aim:

The programmed cell death ligand 1 (PD-L1) is overexpressed by various cancers, resulting in a downregulation of the local immune response and therefore enabling further tumor growth.[1] Immune checkpoint inhibitors (ICIs) can reactivate the immune system, however, only 30% of the patients respond to an ICI monotherapy.[2] Since PD-L1 is heterogeneously expressed within and across tumor sites, there is an urgent clinical need for non-invasive diagnostic tools to support the therapeutic decision process. Small molecule-based radiotracers for noninvasive molecular PD-L1 imaging offer improved tissue penetration, fast blood clearance and low immunogenicity over radiolabeled antibodies.

Methods:

Based on a published small molecule PD-L1 inhibitor, 10 different radioligands were synthesized and radiolabeled with copper-64 (HZDR, 30 MeV TR-FLEX cyclotron). Binding affinities were determined on PC3 cells stably overexpressing human PD-L1. For in vivo evaluation, qualitative PET/CT imaging (nanoSCAN PET/CT, Mediso) was performed in NMRI-FoxN1-nude mice bearing PC3-hPD-L1 xenografted tumors.

Results:

Modification of the PD-L1 binding motif with strongly water-solubilizing sulfonate and phosphonate groups, different linker units and a NODAGA-chelator in 21-25 organic synthesis steps (12-13 longest linear sequence) yielded 10 different ligands [3]. The 64Cu-labelled radiotracers exhibited logD values between -3.17 and -4.15 for six ligands of the first series, with dissociation constants (Kd) between 80.5 and 532.8 nM, as determined by saturation binding assays. Depending on the number and pattern of sulfonate and phosphonate groups, the in vivo experiments showed drastically different pharmacokinetic profiles: Compounds bearing a less hydrophilic linker showed improved tumor uptake. Three sulfonates resulted in increased blood circulation times of up to 24 h due to albumin binding increased renal clearance but also low tumor uptake (SUVmax = 1.4). Substitution of one sulfonate with a phosphonate reduced the circulation time to two hours, however, accompanied by mainly hepatobiliary clearance. To achieve predominant renal clearance, a second series of four compounds bearing two phosphonate and one sulfonate groups in the solubilizer unit and larger halogens at the central aryl core for improved tumor uptake were synthesized and are currently tested in vivo.

Conclusion:

Sulfonate groups in the PD-L1 tracers increased circulation times along with renal clearance, while tracers with one phosphonate group reduced the blood circulation time but lead to a more hepatobiliary clearance. Structural modifications to increase the binding affinity and improve tumor uptake are currently ongoing.

References:

[1] M. A. Postow, M. K. Callahan, J. D. Wolchok, J. Clin. Oncol. 2015, 33, 1974-1982.
[2] S. L. Topalian, C. G. Drake, D. M. Pardoll, Cancer Cell 2015, 27, 450-461.
[3] Stadlbauer S., Krutzek F., Kopka K. EP21212444.0, December 6th 2021.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    20th European Symposium on Radiopharmacy and Radiopharmaceuticals, 24.-27.11.2022, Verona, Italia

Permalink: https://www.hzdr.de/publications/Publ-36023


Small Molecule-Based Radiotracers for PET Imaging of PD-L1 With Copper-64

Krutzek, F.; Donat, C.; Ullrich, M.; Kopka, K.; Stadlbauer, S.

Abstract

Aim/Introduction
The programmed cell death ligand 1 (PD-L1) is expressed by several cancer types and leads to a downregulation of the local immune response, therefore enabling tumour cells to evade the immune response.[1] So-called immune checkpoint inhibitors (ICI) are able to reactivate the immune system, however, only 30% of the patients respond to an ICI monotherapy.[2] Since PD-L1 is heterogeneously expressed within and across tumour sites, there is an urgent clinical need for a diagnostic, non-invasive imaging probe to support therapy decision. Small molecule-based radiotracers for PD-L1 PET or SPECT imaging fulfil these requirements due to their fast clearance, low risk of side effects and highly sensitive imaging at the molecular level.[3]

Materials & Methods
Based on a published small molecule PD-L1 inhibitor, six different radioligands were synthesized and radiolabelled with copper-64 (HZDR, 30 MeV TR-FLEX cyclotron). Binding affinities were determined on PC3 cells stably overexpressing human PD-L1 which were kindly provided by the Department of Radioimmunology. For in vivo evaluation, qualitative PET/CT imaging experiments (nanoSCAN PET/CT scanner, Mediso) were performed in NMRI-FoxN1-nude mice bearing PC3-hPD-L1 xenografted tumours.

Results
We designed six radioligands by modifying the PD-L1 binding motif with strongly water-solubilizing sulfonate and phosphonate groups, hydrophilic linker units and a NODAGA-chelator in 21 – 25 organic synthesis steps (12-13 longest linear sequence).[4] The copper-64 labelled radiotracers exhibited log(D) values between –3.17 and –4.15. Binding affinities (Kd) were between 80.5 and 532.8 nmol/L. Depending on the number and pattern of sulfonate and phosphonate groups, the in vivo experiments showed drastically different pharmacokinetic profiles: The radiotracer containing three sulfonates showed long circulation times of 24 h due to albumin binding, renal clearance but low tumour uptake (SUVmax = 1.4). Substitution of one sulfonate with a phosphonate improved tumour uptake (SUVmax = 3.1), reduced the circulation time to two hours but showed a more hepatobiliary clearance. The less hydrophilic radiotracer in this series with a Kd of 82.4 ± 7.42 nM, bearing one sulfonate and one phosphonate showed the most favourable pharmacokinetic profile with a short circulation time, renal clearance and an increased tumour uptake (SUVmax = 3.5).

Conclusions
The radiotracer bearing one sulfonate and one phosphonate group exhibited the best pharmacokinetic profile. This radioligand will undergo further structural modifications to increase the binding affinity and improve the tumour uptake.

References
[1] M. A. Postow, M. K. Callahan, J. D. Wolchok, J. Clin. Oncol. 2015, 33, 1974-1982.
[2] S. L. Topalian, C. G. Drake, D. M. Pardoll, Cancer Cell 2015, 27, 450-461.
[3] S. Chatterjee, W. G. Lesniak, S. Nimmagadda., Mol. Imaging 2017, 16, 1-5.
[4] S. Stadlbauer, F. Krutzek, K. Kopka, EP21212444.0, 2021.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    35th Annual Congress of the European Association of Nuclear Medicine, 15.-19.10.2022, Barcelona, Espana

Permalink: https://www.hzdr.de/publications/Publ-36022


Small Molecule-Radioliganden für PET-Bildgebung von PD-L1 mit Kupfer-64

Krutzek, F.; Donat, C.; Ullrich, M.; Kopka, K.; Stadlbauer, S.

Abstract

Ziel: Der Programmed Cell Death Ligand 1 (PD-L1) ist auf verschiedenen Tumorentitäten überexprimiert und hemmt die Immunantwort durch Bindung an PD-1 auf T-Zellen. Immuncheckpoint-Inhibitoren können diese Blockade aufbrechen und die Immunantwort reaktivieren. Da nur ca. 30% der Patienten auf eine solche Therapie ansprechen, besteht klinisch ein dringender Bedarf an einem nicht-invasiven PET/SPECT-Radioliganden, um die Ansprechrate der Patienten auf diese Therapie abzuschätzen.[1]

Methoden: Basierend auf den Strukturen von nicht-peptidischen PD-L1-Inhibitoren, wurden sechs verschiedene Radioliganden synthetisiert und mit [64Cu]Cu2+ markiert (HZDR, 30 MeV TR-FLEX-Zyklotron). Bindungsaffinitäten wurden auf stabil hPD-L1 überexprimierenden PC3 Zellen bestimmt. In vivo wurden qualitative PET/CT-Bilder (nanoSCAN PET/CT, Mediso) an NMRI-FoxN1-Nacktmäusen mit PC3-hPD-L1- und mock-Tumoren aufgenommen.

Ergebnisse:

Zwei PD-L1-Inhibitoren wurden synthetisch mit stark wasserlöslichen Säuregruppen, hydrophilen Linkern und NODAGA modifiziert (Abb. 1a).[2] Die LogD7.4-Werte der [64Cu]Cu-Radioliganden lagen zwischen –3,17 und –4,15 und die Bindungsaffinitäten (KD) zwischen 80,5 und 532,8 nM. Abhängig von der Zahl und dem Substitutionsmuster der Sulfon- und Phosphonsäuregruppen, zeigte sich in vivo eine stark unterschiedliche Pharmakokinetik. Der Radioligand mit R1 = SO2Me, R2 = PO3H2 und n = 0 zeigte in vivo eine kurze Zirkulationszeit, renale Ausscheidung, gute Tumoraufnahme (SUVmax = 3.5) und einen deutlichen Kontrast zwischen hPD-L1- und mock-Tumor (Abb. 1b).
Schlussfolgerungen: Der PD-L1-Radioligand mit je einer Sulfon- und Phosphonsäuregruppe wies das beste pharmakokinetische Profil auf. Um die Bindungsaffinität und die Tumoraufnahme zu verbessern, wird das Leitmotiv derzeit weiter modifiziert.

Referenzen:

[1] Postow M. A., Callahan M. K., Wolchok J. D. J. Clin. Oncol. 2015, 33, 1974-1982.
[2] Stadlbauer S., Krutzek F., Kopka K. EP21212444.0, 2021.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    28. Jahrestagung der Arbeitsgemeinschaft Radiochemie / Radiopharmazie, 22.-24.09.2022, Wart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36021


Detection schemes for quantum vacuum diffraction and birefringence

Ahmadiniaz, N.; Cowan, T.; Grenzer, J.; Franchino-Vinas, S.; Laso García, A.; Smid, M.; Toncian, T.; Trejo Espinosa, M. A.; Schützhold, R.

Abstract

Motivated by recent experimental initiatives, such as at the
Helmholtz International Beamline for Extreme Fields (HIBEF)
at the European X-ray Free Electron Laser (XFEL), we calculate
the birefringent scattering of x-rays at the combined field of
two optical (or near-optical) lasers and compare various scenarios.
%
In order to facilitate an experimental detection of quantum vacuum diffraction and
birefringence, special emphasis is placed on scenarios where the initial
and final x-ray photons differ not just in polarization, but also in
propagation direction (corresponding to scattering angles in the mrad regime)
and possibly energy.

Keywords: Strong Field QED; Vacuum qirefringence; Quantum vacuum diffraction; Euler-Heisenberg Lagrangian; XFEL; Laser; Light-by-light scattering

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Permalink: https://www.hzdr.de/publications/Publ-36020


Resummed heat-kernel and form factors for surface contributions: Dirichlet semitransparent boundary conditions

Franchino-Vinas, S.

Abstract

In this article we consider resummed expressions for the heat-kernel's
trace of a Laplace operator, the latter including a potential and imposing Dirichlet semitransparent boundary conditions on a surface of codimension one in flat space.
We obtain resummed expressions that correspond to the first and second order expansion of the heat-kernel in powers of the potential.
We show how to apply these results to obtain the bulk and surface form factors of a scalar quantum field theory in $d=4$ with a Yukawa coupling to a background.
A characterization of the form factors in terms of pseudo-differential operators is given.

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Permalink: https://www.hzdr.de/publications/Publ-36019


Geometrizing the Klein–Gordon and Dirac equations in Doubly Special Relativity

Franchino-Vinas, S.; Relancio, J. J.

Abstract

In this work we discuss the deformed relativistic wave equations, namely the Klein--Gordon and Dirac equations in a Doubly Special Relativity scenario.
We employ what we call a geometric approach, based on the geometry of a curved momentum space, which should be seen as complementary to the more spread algebraic one.
In this frame we are able to rederive well-known algebraic expressions, as well as to treat yet unresolved issues, to wit, the explicit relation between both equations, the discrete symmetries for Dirac particles, the fate of covariance, and the formal definition of a Hilbert space for the Klein--Gordon case.

Keywords: Doubly Special Relativity; Klein-Gordon equation; Dirac equation; Curved momentum space

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Permalink: https://www.hzdr.de/publications/Publ-36017


A hybrid multi-particle approach to range assessment-based treatment verification in particle therapy

Meric, I.; Alagoz, E.; Hysing, L.; Kögler, T.; Lathouwers, D.; Lionheart, W.; Mattingly, J.; Obhodas, J.; Pausch, G.; Pettersen, H.; Ratliff, H.; Rovituso, M.; Schellhammer, S.; Setterdahl, L.; Skjerdal, K.; Sterpin, E.; Sudac, D.; Turko, J. A. B.; Ytre-Hauge, K.

Abstract

Particle therapy (PT) used for cancer treatment can spare healthy tissue and reduce treatment toxicity. However, full exploitation of the dosimetric advantages of PT is not yet possible due to range uncertainties, warranting development of range-monitoring techniques. This study proposes a novel range-monitoring technique introducing the yet unexplored concept of simultaneous detection and imaging of fast neutrons and prompt-gamma rays produced in beam-tissue interactions. A quasi-monolithic organic detector array is proposed, and its feasibility for detecting range shifts in the context of proton therapy is explored through Monte Carlo simulations of realistic patient models. The results indicate that range shifts of 1 mm can be detected at relatively low proton intensities (6 million/spot) when spatial information obtained through imaging of both particle species are used simultaneously. This study lays the foundation for multi-particle detection and imaging systems in the context range verification in PT.

Keywords: particle therapy; treatment verification; fast neutrons; prompt gamma rays; three dimensional imaging

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Permalink: https://www.hzdr.de/publications/Publ-36016


Worldline instantons for the momentum spectrum of Schwinger pair production in space-time dependent fields

Degli Esposti, G.; Torgrimsson, G.

Abstract

We show how to use the worldline-instanton formalism to calculate the momentum spectrum of the electron-positron pairs produced by an electric field that depends on both space and time. Using the LSZ reduction formula with a worldline representation for the propagator in a spacetime field, we make use of the saddle-point method to obtain a semiclassical approximation of the pair-production spectrum. In order to check the final result, we integrate the spectrum and compare with the results obtained using a previous instanton method for the imaginary part of the effective action.

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Permalink: https://www.hzdr.de/publications/Publ-36015


Recovery of Release Cloud from Laser Shock-Loaded Graphite and Hydrocarbon Targets: In Search of Diamonds

Schuster, A. K.; Voigt, K.; Klemmed, B.; Hartley, N. J.; Lütgert, B. J.; Bähtz, C.; Benad, A.; Brabetz, C.; Cowan, T.; Doeppner, T.; Erb, D.; Eychmueller, A.; Facsko, S.; Falcone, R. W.; Fletcher, L. B.; Frydrych, S.; Ganzenmüller, G. C.; Gericke, D. O.; Glenzer, S. H.; Grenzer, J.; Helbig, U.; Hiermaier, S.; Hübner, R.; Laso García, A.; Lee, H. J.; Macdonald, M. J.; McBride, E. E.; Neumayer, P.; Pak, A.; Pelka, A.; Prencipe, I.; Prosvetov, A.; Rack, A.; Ravasio, A.; Redmer, R.; Reemts, D.; Rödel, M.; Schoelmerich, M.; Schumacher, D.; Tomut, M.; Turner, S. J.; Saunders, A. M.; Sun, P.; Vorberger, J.; Zettl, A.; Kraus, D.

Abstract

This work presents first insights into the dynamics of free-surface release clouds from dynamically compressed polystyrene and pyrolytic graphite at pressures up to 200 GPa, where they transform into diamond or lonsdaleite, respectively. These ejecta clouds are released into either vacuum or various types of catcher systems, and are monitored with high-speed recordings (frame rates up to 10 MHz). Molecular dynamics simulations are used to give insights to the rate of diamond preservation throughout the free expansion and the catcher impact process, highlighting the challenges of diamond retrieval. Raman spectroscopy data show graphitic signatures on a catcher plate confirming that the shock-compressed PS is transformed. First electron microscopy analyses of solid catcher plates yield an outstanding number of different spherical-like objects in the size range between ten(s) up to hundreds of nanometres, which are one type of two potential diamond candidates identified. The origin of some objects can unambiguously be assigned, while the history of others remains speculative.

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Permalink: https://www.hzdr.de/publications/Publ-36014


Integrated phycoremediation and ultrasonic-irradiation treatment (iPUT) for the enhanced removal of pharmaceutical contaminants in wastewater

Kurade, M. B.; Mustafa, G.; Zahid, M. T.; Awasthi, M. K.; Chakankar, M. V.; Pollmann, K.; Khan, M. A.; Park, Y. K.; Chang, S. W.; Chung, W.; Jeon, B.-H.

Abstract

Ultrasonication using low frequencies of sound can increase cell organogenesis, which is beneficial for various industrial applications. This study demonstrates a novel approach of integrated phycoremediation and ultrasonication-irradiation treatment (iPUT) used for improving the degradation of sulfonamide antibiotics via a cumulative effect of combined treatments. Variable ultrasonication treatment (UT) (20 %-2 min to 40 %-10 min) was given to a model microalga, Chlamydomonas mexicana in two ways, 1) single ultrasonic treatment (SUT) and 2) multiple-intermittent ultrasonic treatments (IUT). The microalgal growth was slightly affected by SUT, while it significantly inhibited by IUT. The removal of sulfacetamide and sulfapyridine was significantly improved by >1.7-fold and >1.95-fold at 20 % of SUT and IUT treatment, respectively, compared to control. In the case of sulfamethazine, the SUT showed maximum removal (33.5 %) at 20 %, whereas IUT could achieve 27.5 % removal at the same ultrasonication conditions compared to 9.5 % removal in control. The IUT accelerated the degradation of sulfamethoxazole and sulfadimethoxine more than SUT showing a 9- fold and 12- fold increase in the removal of sulfamethoxazole and sulfadimethoxine with 20 % and 40 % treatments, respectively. The changes in microalgal cell morphology due to ultrasonication treatment were the main cause of enforced uptake and subsequent degradation of these ECs.

Keywords: phycoremediation

Permalink: https://www.hzdr.de/publications/Publ-36013


Carborane Analogues of Fenoprofen Exhibit Improved Antitumor Activity

Useini, L.; Mojić, M.; Laube, M.; Lönnecke, P.; Mijatović, S. S.; Maksimović-Ivanić, D.; Pietzsch, J.; Hey-Hawkins, E.

Abstract

Fenoprofen is a widely used nonsteroidal anti-inflammatory drug (NSAID) against rheumatoid arthritis, degenerative joint disease, ankylosing spondylitis and gout. Like other NSAIDs, fenoprofen inhibits the synthesis of prostaglandins by blocking both cyclooxygenase (COX) isoforms, COX-1 the “house-keeping” enzyme and COX-2 the induced isoform from pathological stimuli. Unselective inhibition of both COX isoforms results in many side effects, but off-target effects have also been reported. The steric modifications of the drugs could afford the desired COX-2 selectivity. Furthermore, NSAIDs have shown promising cytotoxic properties. The structural modification of fenoprofen using bulky dicarba-closo-dodecaborane(12) (carborane) clusters and the biological evaluation of the carborane analogues for COX inhibition and antitumor potential showed that the carborane analogues exhibit stronger antitumor potential compared to their respective aryl-based compounds.

Permalink: https://www.hzdr.de/publications/Publ-36012


Investigating Brain Connectivity with Graph Neural Networks and GNNExplainer

Zhdanov, M.; Steinmann, S.; Hoffmann, N.

Abstract

Functional connectivity plays an essential role in modern neuroscience. The modality sheds light on the brain's functional and structural aspects, including mechanisms behind multiple pathologies. One such pathology is schizophrenia which is often followed by auditory verbal hallucinations. The latter is commonly studied by observing functional connectivity during speech processing. In this work, we have made a step toward an in-depth examination of functional connectivity during a dichotic listening task via deep learning for three groups of people: schizophrenia patients with and without auditory verbal hallucinations and healthy controls. We propose a graph neural network-based framework within which we represent EEG data as signals in the graph domain. The framework allows one to 1) predict a brain mental disorder based on EEG recording, 2) differentiate the listening state from the resting state for each group and 3) recognize characteristic task-depending connectivity. Experimental results show that the proposed model can differentiate between the above groups with state-of-the-art performance. Besides, it provides a researcher with meaningful information regarding each group's functional connectivity, which we validated on the current domain knowledge.

Keywords: Graph neural networks; EEG; Functional connectivity

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Permalink: https://www.hzdr.de/publications/Publ-36011


Experimental dosimetric validation of an open-source treatment planning system for IMPT dose delivery at a horizontal PBS research beamline

Sepúlveda, C.; Gebauer, B.; Hoffmann, A. L.; Lühr, A.; Wahl, N.; Burigo, L.

Abstract

Objectives: This study investigates the ability of the open-source treatment planning system (TPS) matRad to generate accurate intensity-modulated proton therapy (IMPT) plans for a real-world horizontal proton pencil beam scanning (PBS) research beamline. Initial validation for IMPT dose delivery is addressed by comparing simulation data with measurements.

Materials and Methods: The PBS delivery was modelled with Monte Carlo (MC) simulations using TOPAS version 3.7. First, base data measurements were performed to develop a proton beam model (BM) for the OncoRay horizontal PBS research beamline. Data include spot sizes in air, depth-dose profiles and a monitor unit (MU) calibration. BM data was then integrated into matRad to build base-data for IMPT treatment planning.
For initial validation of dose delivery, simple 3D box plans were generated at three depths (target beam entrance at 10, 15 and 20cm) covering energies from 115 to 195MeV. Absolute and relative doses were measured using a Semiflex 31013 ionization chamber (PTW Dosimetry) and a scintillation detector (Lynx®, IBA Dosimetry), respectively.

Results: Simulations and dose measurements showed good agreement of relative dose profiles at depths of 14.75, 18.05 and 24.05cm for field sizes of 5 x 5, 10 x 10 and 15 x 15cm2. The overall absolute difference of measured and planned target doses was ~1% (see Table 1).

Conclusions: Accurate MC-based BM was calculated and integrated into the TPS toolkit matRad. Absolute and relative measurements were in agreement with planned IMPT data. Full validation will be completed next months, including absolute and relative dosimetry of patient plans.

Involved research facilities

  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-36009


OPC UA Based User Data Interface at ELBE

Zenker, K.; Justus, M.; Steinbrück, R.

Abstract

The Electron Linac for beams with high Brilliance and low Emittance (ELBE) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is operated using the SCADA system WinCC by Siemens. The majority of ELBE systems is connected to WinCC via industrial Ethernet and proprietary S7 communication. However, in recent years there was a demand to provide a more open and platform independent access to ELBE machine data. The Industry 4.0 standard OPC UA has been chosen to implement such an interface. We will show how we use OPC UA as a common communication layer between industrial and scientific instruments as well as proprietary and open source control system software. Our solution makes use of commercially available hard- and software, namely Simatic STEP7, Simatic WinCC v7.x by Siemens and IBH Link UA by IBHsoftec. Combining these products we designed an OPC UA based user data interface, which features encrypted communication and access control from the control room via WinCC. It is available for internal use, e.g. for feedbacks, and external use, e.g to log ELBE data along with experiment data or to provide data to ELBE operators for machine optimizations.

Keywords: OPC UA

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Related publications

  • Poster
    13th International Workshop on Emerging Technologies and Scientific Facilities Controls, 04.-07.10.2022, Dolní Břežany/Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-36006


X-ray radiation transport in GPU accelerated Particle In Cell simulations

Ordyna, P.; Kluge, T.; Cowan, T.; Schramm, U.

Abstract

Ultra-high-intensity laser pulse interactions with solid density targets are of central importance for
modern accelerator physics, Inertial Confinement Fusion(ICF) and astrophysics. In order to meet
the requirements of real-world applications, a deeper understanding of the underlying plasma
dynamics, including plasma instabilities and acceleration mechanisms, is needed. X-ray radiation
plays a substantial role in plasma physics, either as an integral part of a physical system itself or
as a useful diagnostic, hence it should be included in computational models.
Therefore, we bring a Monte Carlo based X-ray radiation transport module into our Particle In
Cell simulation framework PIConGPU. It allows, among others, for Thompson scattering, e.g. for
small-angle X-ray scattering (SAXS), and Faraday effect calculation for X-ray polarimetry - as
online, in-situ diagnostics.

Involved research facilities

  • HIBEF
  • Poster
    8. Annual MT Meeting, 26.-27.09.2022, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36005


NuScale SMR 3-D modelling and analysis of boron dilution with the system code ATHLET in the framework of McSAFER

Diaz Pescador, E.; Jobst, M.; Kliem, S.

Abstract

The small modular reactor (SMR) NuScale is modelled by Helmholtz-Zentrum Dresden Rossendorf (HZDR) in the framework of the EU H2020 McSAFER. NuScale is a SMR of integral pressurized type operated with light water driven by natural circulation. This work summarizes the reactor modelling approach with the system code ATHLET and presents the results from a boron dilution sequence, based on the Design Certification Application (DCA). Steady-state and transient results show agreement, thereby demonstrating ATHLET strong simulation capabilities on complex transients applied to SMR designs. The results show a decrease in core nominal boron concentration and subsequent reactivity insertion by the boron feedback. The reactor is tripped upon “high pressurizer pressure” setpoint and the actuation of the DHRS leads to a long term safe shutdown condition.

  • Contribution to proceedings
    KERNTECHNIK 2022, 21.06.2022, Leipzig, Germany
  • Lecture (Conference)
    KERNTECHNIK 2022, 21.06.2022, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-36003


NuScale SMR 3-D Modelling and Applied Safety Analyses with the System Code ATHLET in the Framework of the EU H2020 McSAFER

Diaz Pescador, E.; Jobst, M.; Kliem, S.

Abstract

Research and development of small modular reactors (SMRs) is receiving increasing attention by several countries and organizations due to flexibility, cost reduction and advanced safety features. The SMR NuScale is modelled by Helmholtz-Zentrum Dresden Rossendorf (HZDR) in the framework of the EU H2020 McSAFER project. NuScale is a SMR of integral pressurized water reactor (PWR) type, operated with light water driven by natural circulation in all operation modes. This work summarizes the modelling approach of a thermohydraulic model of NuScale SMR with the system code ATHLET, that includes a state-of-the-art 3-D reactor pressure vessel (RPV). The paper presents results and discussion from a boron dilution sequence at hot full power based on the Design Certification Application (DCA) report. Simulation results show agreement at steady-state and transient calculation, thereby demonstrating ATHLET strong simulation capabilities on complex sequences in SMR designs. The results show a decrease in core nominal boron concentration and subsequent reactivity insertion by boron feedback. The reactor is tripped upon “high pressurizer pressure” function by the insertion of the control rod banks. The actuation of the decay heat removal system (DHRS) provides long term core cooling to bring the reactor to a safe shutdown condition and preservation of shutdown margin is met during the simulation thereby complying with acceptance criterion.

Keywords: NuScale; SMR; ATHLET; Boron Dilution; McSAFER

  • Contribution to proceedings
    13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety, 06.09.2022, Hsinchu, Taiwan
  • Lecture (Conference) (Online presentation)
    13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety, 06.09.2022, Hsinchu, Taiwan

Permalink: https://www.hzdr.de/publications/Publ-36001


Nanoparticle depressants in fine particle seperation - The Efeect of Colloidal Silica in Calcium Mineral Flotation

Ben Said, B.; Pereira, L.; Rudolph, M.

Abstract

The micro particle separation of calcium minerals by means of selective froth flotation is a challenging task. The difficulty arises because of the similar surface properties of the minerals, and thereby similar responses to various known families of flotation collectors (selectively adsorbing surfactants). Within the scope of this study colloidal silica is investigated as a potential selectively interacting nanoparticle depressant in the flotation process of calcium minerals. The effect of the colloidal silica and its interactions with the reagent system were investigated by varying its modification and specific surface area/particle size. Single-mineral microflotation of scheelite (calcium tungstate), fluorite (calcium fluoride), calcite (calcium carbonate) and apatite (calcium fluoro phosphate) were used to determine if colloidal silica would have any effect on the minerals. First results show that colloidal silica prevents calcite from floating while scheelite, fluorite and apatite are unaffected by the presence of the reagent, regardless of the dosage.
First batch flotation tests have shown significant differences between the three modifications in terms of the significant effect on the selectivity. The same finding was made when varying the specific surface area/particle size. Further surface chemistry studies will provide more insight on the depression mechanisms of colloidal silica in calcium mineral flotation.

Keywords: Froth Flotation; Nanoparticles; Adsorption; Bubble attachment; Particle interactions

  • Open Access Logo Lecture (Conference)
    9th World Congress on Particle Technology, 18.-22.09.2022, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-35997


Einsatz der FTC-Mini-Pilotanlage zur Optimierung von Flotationsprozessen Vorteile und Grenzen

Ben Said, B.; Pereira, L.; Rudolph, M.

Abstract

Die Aufbereitung komplexer Erze durch neue Verfahren oder durch den Einsatz neuer oder ungewöhnlicher Reagenzien in der Flotation kann Probleme mit sich bringen. Insbesondere wenn neue Flotationsreagenzien verwendet werden oder ein kompliziertes Fließschema erforderlich ist, lassen sich die Auswirkungen auf den Betrieb anhand von Laborversuchen nicht ausreichend bestimmen. Es ist daher ratsam, Erze im kontinuierlichen Betrieb einer Pilotanlage zu untersuchen, bevor eine Aufbereitungsanlage im industriellen Maßstab installiert wird. Üblicherweise sind konventionelle Pilotanlagen, in denen 100 bis 1.000 kg/h Erzproben verarbeitet werden, eingesetzt, um die Machbarkeit des Verfahrens vor dem industriellen Maßstab zu belegen. Daraus ergeben sich detaillierte technische Daten, die für die Entwicklung eines endgültigen Prozessablaufs und die Dimensionierung der Ausrüstung erforderlich sind. Allerdings sind diese Pilotanlagen teuer in der Errichtung und im Betrieb. Als Alternative entwickelte das Falconbridge Technology Centre (FTC) 1999 in Zusammenarbeit mit Canadian Process Technologies Inc. eine Mini-Pilotanlage. Die FTC-Mini-Pilotanlage hat zunehmend an Bedeutung gewonnen, vor allem wegen der geringeren Probenmenge im Vergleich zur konventionellen Pilotanlage. In diesem Beitrag wird anhand der Ergebnisse der Batch-Flotation einer Fallstudie der Einsatz der FTC-Mini-Pilotanlage Optimierung des Flotationsprozesses von Scheelit unter Verwendung ein neuer Drücker aufgezeigt. Die Vorteile und Grenzen des Betriebs der Mini-Pilotanlage werden erörtert und die Ergebnisse im industriellen Maßstab validiert.

Keywords: Anlagenoptimierung; Flotationsprozess; Mineralienaufbereitung; Mini-Pilotanlage; Prozessoptimierung

  • Open Access Logo Lecture (Conference)
    Aufbereitung und Recycling 2022, 10.-11.11.2022, Freiberg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-35996


Surrogate Modeling of Laser-Ion Acceleration in the Near-Critical Density Regime with Invertible Neural Networks

Miethlinger, T.; Garten, M.; Göthel, I.; Hoffmann, N.; Schramm, U.; Kluge, T.

Abstract

The interaction of near-critical plasmas with ultra-intense laser pulses presents a promising approach to enable the development of very compact sources for high-energetic ions. However, current records for maximum proton energies are still below the required values for many applications, and challenges such as stability and spectral control remain unsolved to this day. In particular, significant effort per experiment and a high-dimensional design space renders naive sampling approaches ineffective. Furthermore, due to the strong nonlinearities of the underlying laser-plasma physics, synthetic observations by means of particle-in-cell (PIC) simulations are computationally very costly, and the maximum distance between two sampling points is strongly limited as well. Consequently, in order to build useful surrogate models for future data generation and experimental understanding and control, a combination of highly optimized simulation codes (we employ PIConGPU), powerful data-based methods, such as artificial neural networks, and modern sampling approaches are essential. Specifically, we employ invertible neural networks for bidirectional learning of parameter and observables, and autoencoder to reduce intermediate field data to a lower-dimensional latent representation.

Keywords: Invertible Neural Networks; Inverse Problems; Laser-Plasma; Laser-Ion Acceleration

  • Lecture (Conference) (Online presentation)
    DPG Spring Meeting Mainz 2022, 28.03.-01.04.2022, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35995


Surrogate Modeling of Laser-Plasma-Based Ion Acceleration with Invertible Neural Networks

Miethlinger, T.; Hoffmann, N.; Kluge, T.

Abstract

The interaction of overdense and/or near-critical plasmas with ultra-intense laser pulses presents a promising approach to enable the development of very compact sources for high-energetic ions. However, current records for maximum proton energies are still below the required values for many applications, and challenges such as stability and spectral control remain unsolved to this day. In particular, significant effort per experiment and a high-dimensional design space renders naive sampling approaches ineffective. Furthermore, due to the strong nonlinearities of the underlying laser-plasma physics, synthetic observations by means of particle-in-cell (PIC) simulations are computationally very costly, and the maximum distance between two sampling points is strongly limited as well. Consequently, in order to build useful surrogate models for future data generation and experimental understanding and control, a combination of highly optimized simulation codes (we employ PIConGPU), powerful data-based methods, such as artificial neural networks, and modern sampling approaches are essential. Specifically, we employ invertible neural networks for bidirectional learning of parameter and observables, and autoencoder to reduce intermediate field data to a lower-dimensional latent representation.

Keywords: Invertible Neural Networks; Inverse Problems; Laser-Plasma; Laser-Ion Acceleration

  • Poster
    Platform for Advanced Scientific Computing 2022, 27.-29.06.2022, Basel, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-35994


Acceptance Rates of Invertible Neural Networks on Electron Spectra from Near-Critical Laser-Plasmas: A Comparison

Miethlinger, T.; Hoffmann, N.; Kluge, T.

Abstract

While the interaction of ultra-intense ultra-short laser pulseswith near- and overcritical plasmas cannot be directly observed, experimentally accessible quantities (observables) often only indirectly giveinformation about the underlying plasma dynamics. Furthermore, theinformation provided by observables is incomplete, making the inverseproblem highly ambiguous. Therefore, in order to infer plasma dynamicsas well as experimental parameter, the full distribution over parameters given an observation needs to considered, requiring that models areflexible and account for the information lost in the forward process. Invertible Neural Networks (INNs) have been designed to efficiently modelboth the forward and inverse process, providing the full conditional posterior given a specific measurement. In this work, we benchmark INNsand standard statistical methods on synthetic electron spectra. First, weprovide experimental results with respect to the acceptance rate, whereour results show increases in acceptance rates up to a factor of 10. Additionally, we show that this increased acceptance rate also results in anincreased speed-up for INNs to the same extent. Lastly, we propose acomposite algorithm that utilizes INNs and promises low runtimes whilepreserving high accuracy.

Keywords: Invertible Neural Networks; Inverse Problems; Machine Learning; Particle-in-Cell; Laser-Plasma Physics

  • Open Access Logo Contribution to WWW
    https://arxiv.org/abs/2212.05836
    DOI: 10.48550/arXiv.2212.05836
    arXiv: 2212.05836
  • Open Access Logo Lecture (Conference)
    14th International Conference on Parallel Processing and Applied Mathematics, 11.-14.09.2022, Gdańsk, Polska
  • Open Access Logo Contribution to proceedings
    14th International Conference on Parallel Processing and Applied Mathematics, PPAM 2022, 11.-14.09.2022, Gdansk, Poland
    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 273-284
    DOI: 10.1007/978-3-031-30445-3_23

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Permalink: https://www.hzdr.de/publications/Publ-35993


Effects of geometry on antiferromagnetic textures: boundaries and geometric curvature

Pylypovskyi, O.; Borysenko, Y.; Tomilo, A.; Kononeko, D.; Yershov, K.; Roessler, U.; Faßbender, J.; van den Brink, J.; Sheka, D.; Makarov, D.

Abstract

Geometric curvature in nanowires and shells is established as a powerful method to tailor chiral and anisotropic responses in ferromagnets. Here, we apply the framework of curvilinear magnetism to antiferromagnetic (AFM) systems. First, we consider curvilinear AFM spin chains with the nearest-neighbor exchange and hard axis of anisotropy along the chain. Their shape is characterized by curvature K and torsion T. These functions determine the direction of the geometry-driven Dzyaloshinskii vector D and easy axis of anisotropy stemming from exchange. Furthermore, the broken translation symmetry in AFM chains arranged along space curves leads to the weakly ferromagnetic response proportional to K and T even if the magnetic texture is locally homogeneous. While the plane AFM chains possess the uniform ground state, the geometry-induced anisotropy axes and chiral response become pronounceable approaching spin-flop phase. Namely, in AFM rings the non-zero D leads to the appearance of canted state for the large enough K, while spin-flop phase splits in two phases by the value of K with different topology of the order parameter. For 3D chiral AFMs, the sample boundaries alter the width and produce an additional twist of domain walls and skyrmions near the surface.

O. V. Pylypovskyi, D. Y. Kononenko, K. V. Yershov et al, Nano Lett. 20, 8157 (2020)
O. V. Pylypovskyi, Y. A. Borysenko, J. Fassbender et al, Appl. Phys. Lett. 118, 182405 (2021)
O. V. Pylypovskyi, A. V. Tomilo, D. D. Sheka et al, Phys. Rev. B 103, 134413 (2021)
Y. A. Borysenko, D. D. Sheka, J. Fassbender et al, ArXiv:2208.02510 (2022)

Keywords: antiferromagnetism; curvilinear spin chains; spin-flop

  • Lecture (Conference) (Online presentation)
    APS March Meeting, 20.-22.03.2023, Online participation, USA

Permalink: https://www.hzdr.de/publications/Publ-35992


Flexomagnetism of thin Cr2O3 films

Makushko, P.; Kosub, T.; Pylypovskyi, O.; Hedrich, N.; Li, J.; Pashkin, O.; Avdoshenko, S.; Hübner, R.; Ganss, F.; Wolf, D.; Lubk, A.; Liedke, M. O.; Butterling, M.; Wagner, A.; Wagner, K.; Shields, B. J.; Lehmann, P.; Veremchuk, I.; Faßbender, J.; Maletinsky, P.; Makarov, D.

Abstract

Cr2O3 is the only known uniaxial antiferromagnetic material that is also magnetoelectric at room temperature. This renders Cr2O3 a technologically relevant playground for the realisation of different device ideas for prospective antiferromagnetic spintronics. We discovered the presence of flexomagnetic effects in Cr2O3, which come about due to the impact of a strain gradient on the thermodynamic properties, namely on the Neel temperature. By combining magnetotransport and Nitrogen Vacancy magnetometry characterizations, we experimentally determine the presence of the gradient of the Neel temperature in a 50-nm-thick Cr2O3 thin film and quantify that the magnetic moment, generated by this new effect, can be as high as 15 μB/nm2. Furthermore, due to good oxide-oxide heteroepitaxy and respective compressive strain, the Neel temperature in Cr2O3 thin films can be enhanced persistently up to 100degC, which is 60degC higher than the bulk transition temperature. The emergent flexomagnetism-driven ferromagnetic order parameter in antiferromagnetic thin films offers more flexibility in the design of spintronic and magnonic devices and can be of relevance for other antiferromagnetic materials.

P. Makushko, T. Kosub, O. V. Pylypovskyi et al., Nature Communications (2022), in press.

Keywords: antiferromagnetism; flexomagnetism; Neel temperature

  • Lecture (Conference) (Online presentation)
    APS March Meeting, 20.-22.03.2023, Online participation, USA

Permalink: https://www.hzdr.de/publications/Publ-35991


(Data set) Distinction of charge transfer and Frenkel excitons in pentacene traced via infrared spectroscopy

Pinteric, M.; Roh, S.; Hammer, S.; Pflaum, J.; Dressel, M.; Uykur, E.

Abstract
  1. Data from the publication are given in Origin format with Figure codes.
  2. More data are available upon request.

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Permalink: https://www.hzdr.de/publications/Publ-35990


Distinction of charge transfer and Frenkel excitons in pentacene traced via infrared spectroscopy

Pinteric, M.; Roh, S.; Hammer, S.; Pflaum, J.; Dressel, M.; Uykur, E.

Abstract

Infrared spectroscopy studies on pentacene single crystals have been performed in the frequency range of 12 meV to 3 eV in reflection and transmission configurations as a function of temperature, down to 10 K. Our results reveal the dominant contributions of the excitonic bands at the absorption edge. The singlet transitions of the Frenkel excitons at 1.78 eV with 130 meV Davydov splitting have been identified. An additional excitonic feature observed at 1.83 eV can be assigned to a charge-transfer type exciton evidenced by the strong vibrational anomalies. On the other hand, the strong feature seen at 1.67 eV does not couple to the vibrational modes suggests that electronic origin in nature.

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Permalink: https://www.hzdr.de/publications/Publ-35989


(Data set)High-pressure investigations in CH3NH3PbX3 ( X = I, Br, and Cl): Suppression of ion migration and stabilization of low-temperature structure

Chan, Y. T.; Elliger, N.; Klis, B.; Kollar, M.; Horvath, E.; Forro, L.; Dressel, M.; Uykur, E.

Abstract

The raw data can be obtained from the corresponding author
Martin Dressel: dressel@pi1.physik.uni-stuttgart.de

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Permalink: https://www.hzdr.de/publications/Publ-35988


Untersuchung zur Flotation von ultrafeinen Partikeln im neu entworfenen Trennapparat MultiDimFlot

Stefenelli, N.

Abstract

Die Flotation ist ein Trennprozess, der in der Aufbereitung und Veredelung eines breiten Spektrums primärer Rohstoffe (Erze, Kohle, Karbonate etc.) sowie in diversen Recyclingprozessen eingesetzt wird [1]. Aufgrund des steigenden Bedarfs an Rohstoffen steht die Aufbereitungstechnik vor der Herausforderung fein- und feinstverwachsene Erze zu flotieren [2]. Daher ist es von großer Bedeutung die Grenzen der Flotierbarkeit in den ultrafeinen Bereich zu erweitern. Bei der Flotation handelt es sich um einen Nassprozess, dessen Trennprinzip auf der unterschiedlichen Benetzbarkeit der zu trennenden Feststoffpartikeln basiert. Hydrophobe Teilchen haften hierbei an eingebrachten Gasblasen und bilden Partikel-Blasen-Aggregate, die in der Suspension aufsteigen und einen Schaum bilden. Diese mit Wertstoff beladene Schaumschicht wird als Konzentrat von der Trübeoberfläche abgezogen. Die hydrophilen Partikel verbleiben hingegen in der Trübe [3]. In der Feinkornaufbereitung mit einem Partikelgrößenbereich von 10 μm bis 200 μm ist dieser Trennprozess weit verbreitet [4]. Die Flotation ultrafeiner Partikel mit einer Größe x < 10 μm stellt jedoch eine Vielzahl an verfahrenstechnischen Herausforderungen dar, sodass die herkömmlichen Flotationsapparate (mechanische Flotationsapparate, Flotationssäulen) entweder nicht oder nur ineffizient das hydrophile Gangmineral vom hydrophoben Wertstoff trennen. Im Rahmen des Projekts MultiDimFlot, welches Teil des DFG Schwerpunktprogramms 2045 MehrDimPart ist, wurde ein spezieller Trennapparat entwickelt, mit dem die Flotation ultrafeiner Partikel untersucht werden soll. Diese Apparatur kombiniert die Vorzüge des turbulenten Strömungsregimes in einer mechanischen Flotationszelle mit dem für die Flotationssäulen typischen tiefen Schaum. Die Flotierbarkeit eines binären Gemisches aus ultrafeinem Magnetit und Glaspartikel mit der MultiDimFlot-Apparatur wird im Zuge dieser Bachelor-Arbeit experimentell untersucht. Der Einfluss variierender Partikeleigenschaften auf den Flotationsprozess wird erforscht, weshalb Glaspartikel mit unterschiedlichen Partikelformen (Sphären, Fragmente und Fasern) und Hydrophobierungszuständen (nicht-, mäßig- und stark hydrophobiert) in Flotationsversuchen verwendet werden. Die experimentelle Arbeit umfasst drei Teile: Das Ziel des ersten Teils ist es, durch Variation der Parameter Rotordrehzahl und Luftzufuhr, geeignete Maschinen-parameter zur Flotation mäßig hydrophobierter, ultrafeiner Fragmente mit der MultiDimFlot-Apparatur zu finden. Im zweiten Teil wird mit den gewählten Betriebsparametern das Flotationsverhalten der übrigen Partikelsysteme untersucht. Der dritte Teil umfasst erste Testversuche zur Herstellung eines stationären Zustands und die Beprobung der Schaumsäule in unterschiedlichen Höhen.

  • Bachelor thesis
    TUBAF, 2022

Permalink: https://www.hzdr.de/publications/Publ-35987


Enhancing magnetic field support for the electrodeposition of nano-structured metal layers by reducing global cell flow

Huang, M.; Skibinska, K.; Zabinski, P.; Eckert, K.; Mutschke, G.

Abstract

Magnetic fields could be a helpful tool for improving the growth of nanostructures on metal layers during electrodeposition processes. It is well known that an electrode-normal magnetic field promotes the growth of mm-sized conical structures by generating a supportive local electrolyte flow. However, we found recently that for smaller cones of μm/nm-size, this local flow may often be superseded by a stronger global cell flow, thus preventing the structuring effect. We therefore discuss improved cell setups to minimize the global flow and to enable the magnetic support of conical growth.

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Permalink: https://www.hzdr.de/publications/Publ-35986


Development of a system for the design and synthesis of tailor-made peptides for the treatment of polymers prior to plastic metallization

Kießlich, T.; Braun, R.; Lederer, F.; Pollmann, K.

Abstract

Increasing demands in environmental protection and environmentally friendly solutions are important market drivers for the development of sustainable chemicals. Chromium (VI) is used in electroplating technology to pretreat polymers in order to achieve good metallization. However, it´s application requires special permits now. This is an EU strategy to prevent the use of dangerous and unhealthy Reduce substances. Finding replacements with conventional chemicals is increasingly difficult. In order to change the chemistry and microstructure of polymer surfaces at suitable temperatures and process times, very reactive chemicals are required, which pose a high risk. Currently available alternative Chromium (VI) -free technologies for polymer preconditioning have not yet been reach the industrial requirements.
One strategy to solve this problem is to focus on very specific and selective reactions. The main aim of this work is to develop a biological system that enables the development and synthesis of tailor-made, selective polymer-binding peptides. The system is based on what is known as phage surface display technology (PSD).
PSD generally uses a library of about 109 phages with various peptides fused to the phage coat proteins. All the phages in the library are unique. Phage particles are incubated with the target material (polymer) in three biopanning cycles. Only a few phages bind to surfaces and the unbound phage particles are removed when the target materials are washed. Finally, the attached phage particles were eluted and amplified in Escherichia coli cells. After the last cycle of biopanning, there are only a few individual phages left that have exceptionally high surface affinity. The phage particles are used for subsequent sequencing, modification and application. The peptides that are expressed by the selected phages are then characterized with regard to their sequence, their binding motif and their interaction with the target material.
.

  • Poster
    European Peptide Symposium, 29.08.-02.09.2022, Sitges, Spanien

Permalink: https://www.hzdr.de/publications/Publ-35984


Covid-19 Infections in Czechia

Abdussalam, W.

Abstract

We provide post-processing data of daily infected COVID-19 cases for a municipality (Obec) level. The current data for municipality level is prepared on Czech_Obec_COVID19_Infections.csv. The file consists of five columns such as region, name, date, infected and population. The region denotes the ID of a county/state followed by its name in the next column. The inserted date of data is prepared in the third column followed by the number of dead and infected cases. Last but not least, the population of the county is provided in the last column.

This data hub was partially funded by the Where2Test project, which is financed by SMWK with tax funds on the basis of the budget approved by the Saxon State Parliament. This data hub was also partially funded by the Center of Advanced Systems Understanding (CASUS) which is financed by Germany’s Federal Ministry of Education and Research (BMBF) and by the Saxon Ministry for Science, Culture and Tourism (SMWK) with tax funds on the basis of the budget approved by the Saxon State Parliament.

Keywords: Covid-19; Czechia

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Permalink: https://www.hzdr.de/publications/Publ-35983


Seeded FEL lasing of the COXINEL beamline driven by the HZDR plasma accelerator

Labat, M.; Couperus Cabadağ, J. P.; Ghaith, A.; Irman, A.; Berlioux, A.; Berteaud, P.; Blache, F.; Bock, S.; Bouvet, F.; Briquez, F.; Chang, Y.-Y.; Corde, S.; Debus, A.; de Oliveira, C.; Duval, J.-P.; Dietrich, Y.; El Ajjouri, M.; Eisenmann, C.; Gautier, J.; Gebhardt, R.; Grams, S.; Helbig, U.; Herbeaux, C.; Hubert, N.; Kitegi, C.; Kononenko, O.; Kuntzsch, M.; La Berge, M.; Le, S.; Leluan, B.; Loulergue, A.; Malka, V.; Marteau, F.; Huy N. Guyen, M.; Oumbarek-Espinos, D.; Pausch, R.; Pereira, D.; Püschel, T.; Ricaud, J.-P.; Rommeluere, P.; Roussel, E.; Rousseau, P.; Schöbel, S.; Sebdaoui, M.; Steiniger, K.; Tavakoli, K.; Thaury, C.; Ufer, P.; Valleau, M.; Vandenberghe, M.; Veteran, J.; Schramm, U.; Couprie, M.-E.

Abstract

Laser Plasma Accelerators (LPAs), harnessing gigavolt-per-centimeter accelerating fields, can generate high peak current, low emittance and GeV class electron beams paving the way for the realization of future compact free-electron lasers (FELs). Here, we report on the commissioning of the COXINEL beamline driven by the HZDR plasma accelerator and experimental demonstration of FEL lasing at 270 nm in a seeded configuration. Control over the radiation wavelength is achieved with an improved bandwidth stability. Furthermore, the appearance of interference fringes, resulting from the interaction between the phase-locked emitted radiation and the seed, confirms longitudinal coherence, representing a key feature of such a seeded FEL. These results are cross-checked with simulations, ELEGANT for beam optics and GENESIS for FEL radiation. We anticipate a navigable pathway toward smaller-scale free-electron lasers at extreme ultra-violet wavelengths.

Keywords: free electron laser; laser plasma accelerator; seeded FEL driven by LPA beams

Involved research facilities

  • Draco
  • Lecture (Conference)
    Advanced Accelerator Concepts (AAC), 06.-11.11.2022, Long Island, New York, USA
  • Invited lecture (Conferences)
    BLIN, 12.10.2022, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35982


Seeded free-electron laser driven by a compact laser plasma accelerator

Labat, M.; Couperus Cabadağ, J. P.; Ghaith, A.; Irman, A.; Berlioux, A.; Berteaud, P.; Blache, F.; Bock, S.; Bouvet, F.; Briquez, F.; Chang, Y.-Y.; Corde, S.; Debus, A.; de Oliveira, C.; Duval, J.-P.; Dietrich, Y.; El Ajjouri, M.; Eisenmann, C.; Gautier, J.; Gebhardt, R.; Grams, S.; Helbig, U.; Herbeaux, C.; Hubert, N.; Kitegi, C.; Kononenko, O.; Kuntzsch, M.; La Berge, M.; Le, S.; Leluan, B.; Loulergue, A.; Malka, V.; Marteau, F.; Huy N. Guyen, M.; Oumbarek-Espinos, D.; Pausch, R.; Pereira, D.; Püschel, T.; Ricaud, J.-P.; Rommeluere, P.; Roussel, E.; Rousseau, P.; Schöbel, S.; Sebdaoui, M.; Steiniger, K.; Tavakoli, K.; Thaury, C.; Ufer, P.; Valleau, M.; Vandenberghe, M.; Veteran, J.; Schramm, U.; Couprie, M.-E.

Abstract

Seeded free-electron laser driven by a compact laser plasma accelerator
Free-electron lasers generate high-brilliance coherent radiation at
wavelengths spanning from the infrared to the X-ray domains. The recent
development of short-wavelength seeded free-electron lasers now allows
for unprecedented levels of control on longitudinal coherence, opening
new scientific avenues such as ultra-fast dynamics on complex systems
and X-ray nonlinear optics. Although those devices rely on state-of-the-art
large-scale accelerators, advancements on laser-plasma accelerators, which
harness gigavolt-per-centimetre accelerating fields, showcase a promising
technology as compact drivers for free-electron lasers. Using such
footprint-reduced accelerators, exponential amplification of a shot-noise
type of radiation in a self-amplified spontaneous emission configuration
was recently achieved. However, employing this compact approach for the
delivery of temporally coherent pulses in a controlled manner has remained
a major challenge. Here we present the experimental demonstration
of a laser-plasma accelerator-driven free-electron laser in a seeded
configuration, where control over the radiation wavelength is accomplished.
Furthermore, the appearance of interference fringes, resulting from the
interaction between the phase-locked emitted radiation and the seed,
confirms longitudinal coherence. Building on our scientific achievements,
we anticipate a navigable pathway to extreme-ultraviolet wavelengths,
paving the way towards smaller-scale free-electron lasers, unique tools for a
multitude of applications in industry, laboratories and universities.

Keywords: free electron laser; laser plasma accelerator; seeded FEL driven by LPA beams

Involved research facilities

  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-35981


Stable and High-Quality Electron Beams from Staged Laser and Plasma Wakefield Accelerators

Foerster, F. M.; Döpp, A.; Haberstroh, F.; Grafenstein, K. V.; Campbell, D.; Chang, Y.-Y.; Corde, S.; Couperus Cabadağ, J. P.; Debus, A.; Gilljohann, M. F.; Habib, A. F.; Heinemann, T.; Hidding, B.; Irman, A.; Irshad, F.; Knetsch, A.; Kononenko, O.; Martinez De La Ossa, A.; Nutter, A.; Pausch, R.; Schilling, G.; Schletter, A.; Schöbel, S.; Schramm, U.; Travac, E.; Ufer, P.; Karsch, S.

Abstract

We present experimental results on a plasma wakefield accelerator (PWFA) driven by high-current
electron beams from a laser wakefield accelerator (LWFA). In this staged setup stable and high-quality
(low-divergence and low energy spread) electron beams are generated at an optically generated hydro-
dynamic shock in the PWFA. The energy stability of the beams produced by that arrangement in the PWFA
stage is comparable to both single-stage laser accelerators and plasma wakefield accelerators driven by
conventional accelerators. Simulations support that the intrinsic insensitivity of PWFAs to driver energy
fluctuations can be exploited to overcome stability limitations of state-of-the-art laser wakefield
accelerators when adding a PWFA stage. Furthermore, we demonstrate the generation of electron bunches
with energy spread and divergence superior to single-stage LWFAs, resulting in bunches with dense phase
space and an angular-spectral charge density beyond the initial drive beam parameters. These results
unambiguously show that staged LWFA-PWFA can help to tailor the electron-beam quality for certain
applications and to reduce the influence of fluctuating laser drivers on the electron-beam stability. This
encourages further development of this new class of staged wakefield acceleration as a viable scheme
toward compact, high-quality electron beam sources.

Keywords: hybrid lwfa-pwfa

Involved research facilities

  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-35980


Theranostic platform technologies for therapy and imaging

Feldmann, A.

Abstract

Theranostic platform technologies for therapy and imaging

Keywords: theranostic; CAR T cell therapy; antibody

  • Invited lecture (Conferences)
    I&I retreat 2022, 09.-10.06.2022, Bonn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35978


Theranostic Antibody- and CAR-based Platform Technology for Therapy and Imaging

Feldmann, A.

Abstract

Theranostic Antibody- and CAR-based Platform Technology for Therapy and Imaging

Keywords: bispecific antibody; CAR T cell therapy; theranostics; UniCAR; RevCAR

  • Invited lecture (Conferences)
    Antibody Technologies and Therapeutics Conference, 11.-14.09.2022, Prato, Italien

Permalink: https://www.hzdr.de/publications/Publ-35977


Adaptor UniCAR and RevCAR platforms for flexible, switchable and combinatorial tumor targeting

Feldmann, A.; Loureiro, L. R.; Kegler, A.; Arndt, C.; Mitwasi, N.; Bergmann, R.; Koristka, S.; Hoffmann, A.; González Soto, K. E.; Kittel-Boselli, E.; Bartsch, T.; Drewitz, L.; Berndt, N.; Fasslrinner, F.; Bornhäuser, M.; Bachmann, M.

Abstract

Chimeric antigen receptor (CAR) T-cells show remarkable therapeutic effects especially in B-cell derived leukemias and lymphomas. However, clinical translation of such an innovative immunotherapeutic approach in highly heterogeneous hematological malignancies like acute myeloid leukemia (AML) or solid tumors is still challenging due to life-threatening side effects, immune escape and disease relapse. To overcome such major hurdles and to address the unmet need for further improvements in CAR therapy, we have established flexible, switchable and programmable adaptor CAR platform technologies named UniCAR and RevCAR. These modular strategies consist of T-cells engineered with adaptor CARs which are primarily inactive as they are incapable to recognize surface antigens. Universal adaptor CAR T-cells can be flexibly redirected to any tumor antigen and controlled by targeting modules (TMs) cross-linking adaptor CAR T- and tumor cells resulting in tumor cell lysis. As an advancement of UniCARs, RevCARs lack the extracellular antigen-binding moiety reducing the receptor size and facilitating the genetical modification of T-cells with several RevCARs possessing different specificity and functionality. Thus, the RevCAR platform enables combinatorial tumor targeting following Boolean logic gates. So far, we have successfully shown preclinical applicability of the UniCAR and RevCAR approaches to target hematological malignancies as well as solid tumors in a flexible and specific manner using tumor cell lines and patient-derived materials. Remarkably, efficiency and switchability of UniCAR T-cells were even proven for the first time in patients in a clinical phase I study. Furthermore, by targeting of two different tumor antigens, combinatorial OR and AND gate logic targeting according to the rules of Boolean algebra was accomplished using the RevCAR platform. These achievements have a high potential for an improved and personalized tumor immunotherapy.

Keywords: UniCAR; RevCAR; CAR T cell therapy; combinatorial tumor targeting

  • Invited lecture (Conferences)
    3rd International Conference on Lymphocyte Engineering, 31.03.-02.04.2022, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35976


Mu2e Run I Sensitivity Projections for the Neutrinoless Muon to Electron Conversion Search in Aluminum

Abdi, F.; Abrams, R.; Adentunji, J.; Ahmed, W.; Alber, R.; Alexander, D.; Allen, D.; Allspach, D.; Alvarez-Garcia, C.; Ambrose, D.; Ambrosio, G.; Amirkhanov, A.; Andreev, N.; Ankenbrandt, C. M.; Appleby, R.; Arnold, D.; Artikov, A.; Atanov, N.; Badgley, K.; Ball, M.; Baranov, V.; Barker, J.; Barnes, E.; Barton, B.; Bartoszek, L.; Bellettini, G.; Bernstein, R. H.; Bersani, A.; Bianchi, I.; Biery, K.; Bini, S.; Blazey, G.; Bloise, C.; Boedigheimer, K.; Boi, S.; Bolton, T.; Bono, J.; Bonventre, R.; Borghi, S.; Borrel, L.; Bossert, R.; Bowcock, T.; Bowden, M.; Brandt, J.; Breach, M.; Brown, D.; Brown, D. N.; Brown, G.; Brown, H.; Budagov, I.; Buelher, M.; Bulugean, G.-M.; Byrum, K.; Campbell, M.; Cao, H.; Carey, R. M.; Caron, J. F.; Casey, B.; Casler, H.; Cervelli, F.; Cheban, S.; Chen, J.; Chen, M.; Cheng, C.-H.; Chislett, R.; Chitirasreemadam, N.; Chokheli, D.; Ciampa, K.; Ciolini, R.; Coghill, J.; Colao, F.; Coleman, R. N.; Corrodi, S.; Crescimbeni, L.; Crowley, C.; Culbertson, R.; Cummings, M. A. C.; Daniel, A.; Davydov, Y.; Demers, S.; Deshpande, A.; Devilbiss, M.; Dey, J.; Defelice, G.; de Gouvea, A.; Dhanraj, J.; Ding, D.; Ding, D.; Dinnon, M.; Diociaiuti, E.; Dixon, S.; Di Falco, S.; Djilkibaev, R.; Donati, S.; Drake, G.; Drendel, B.; Duerling, G.; Dukes, E. C.; Dychkant, A.; Echenard, B.; Eddy, N.; Edmonds, A.; Ehrlich, R.; Ekka, U.; Evans, R.; Evbota, D.; Fabbricatore, P.; Fagan, J.; Farinon, S.; Farrell, W.; Farris, P.; Feher, S.; Fellenz, B.; Fernandez, E.; Ferrari, A.; Ferrari, C.; Finley, J.; Flood, K.; Flumerfelt, E.; Fontana, F.; Francis, K.; Frand, M.; Frank, M.; Friedsam, H.; Gallo, G.; Gandrajula, R. P.; Gaponenko, A.; Gardner, M.; Gargiulo, R.; Gaugel, S.; Genser, K. L.; Gersabeck, M.; Ginther, G.; Gioiosa, A.; Giovannella, S.; Giusti, V.; Glagolev, V.; Glass, H.; Glenzinski, D. A.; Goadhouse, S.; Goodenough, L.; Grancagnolo, F.; Gray, P.; Group, C.; Hahn, A.; Hampai, D.; Hansen, S.; Happacher, F.; Harkness-Brennan, L.; Harrig, K.; Hartsell, B.; Hays, S.; Hedges, M.; Hedin, D.; Heller, K.; Herman, A.; Hirsh, S.; Hitlin, D. G.; Hocker, A.; Hooper, R.; Horton-Smith, G.; Huang, S.; Huedem, E.; Huffman, D.; Hung, P. Q.; Hungerford, E.; Ibrahim, A.; Israel, S.; Jenkins, M.; Johnstone, C.; Jones, M.; Jorjadze, V.; Judson, D.; Kampa, C.; Kargiantoulakis, M.; Kashikhin, V.; Kasper, P.; Keshavarzi, A.; Khalatian, V.; Kim, J.-H.; Kiper, T.; Knapp, D.; Knodel, O.; Knoepfel, K.; Kokosa, L.; Kolomensky, Y. G.; Koltick, D.; Kozlovsky, M.; Kozminski, J.; Kracczyk, G.; Kramp, M.; Krave, S.; Krempetz, K.; Kutschke, R. K.; Kwarciany, R.; Lackowski, T.; Lamm, M. J.; Lancaster, M.; Larwill, M.; Leavell, F.; Lee, M. J.; Leeb, D.; Lema-Sinchi, J.; Leveling, T.; Lewis, R.; Ley, A.; Li, B.; Li, Y.; Lin, D.; Lincoln, D.; Logashenko, I.; Lombardo, V.; Lopes, M. L.; Luca, A.; Lynch, K. R.; Mackenzie, M.; Makulski, A.; Manolis, J.; Maravin, Y.; Marciano, W. J.; Marini, A.; Martin, E.; Martinez, A.; Martini, M.; McArthur, D.; McConologue, F.; Mesmer, N.; Messerly, B.; Michelotti, L.; Middleton, S.; Miles, C.; Miller, J. P.; Miscetti, S.; Mitchell, D.; Miyashita, T.; Mokhov, N.; Molenaar, D.; Molzon, W.; Moore, J.; Morescalchi, L.; Morgan, J.; Mott, J.; Motuk, E.; Müller, S.; Mukherjee, A.; Murat, P.; Musenich, R.; Nagaslaev, V.; Narayanan, A.; Neely, R.; Neuffer, D. V.; Nguyen, M. T.; Nicol, T.; Niehoff, J.; Nogiec, J.; Norman, A.; Northrup, K.; O'Dell, V.; Oh, S.; Oksuzian, Y.; Olderr, P.; Olson, M.; Orris, D.; Oshinowo, B.; Ostojic, R.; Oyang, J.; Paesani, D.; Pagan, S.; Page, T.; Palladino, A.; Park, C.; Pasciuto, D.; Pedreschi, E.; Peterson, T.; Pezzullo, G.; Pilipenko, R.; Pla-Dalmau, A.; Plesniak, P.; Pohlman, N.; Pollack, B.; Poloubotko, V.; Popovic, M.; Popp, J. L.; Porter, F.; Prebys, E. J.; Price, J.; Prieto, P.; Pronskikh, V.; Pushka, D.; Quirk, J.; Rabehl, R.; Rachamin, R.; Raffaelli, F.; Ragheb, A.; Rakness, G.; Ray, R. E.; Rechenmacher, R.; Rivera, R.; Rizzo, G.; Roberts, B. L.; Roberts, S.; Roberts, T. J.; Robotham, W.; Roehrken, M.; Rubinov, P.; Rucinski, R.; Rusu, V. L.; Samavat, M. F.; Sanzani, E.; Saputi, A.; Sarra, I.; Sarychev, M.; Scarpine, V.; Schappert, W.; Schmitt, M.; Schmitter, P.; Schoo, D.; Schumacher, K.; Shi, X.; Singh, V.; Sobering, T.; Soleti, R.; Solt, M.; Song, H.; Song, E.; Spinella, F.; Srivastav, M.; Stefanik, A.; Stetzler, S.; Still, D.; Stortini, M.; Stratakis, D.; Strauss, T.; Sun, Y.; Suslov, I.; Syphers, M. J.; Szemraj, L.; Ta, J.; Taffara, A.; Tang, Z.; Tanovic, N.; Tartaglia, M.; Tassielli, G.; Taylor, R.; Tecchio, M.; Tickle, S.; Tinsley, D.; Tope, T.; Torkelson, A.; Tran, N.; Trevor, J.; Tschirhart, R. S.; Turnberg, S.; Uzunyan, S.; Varier, D.; Varier, D.; Velasco, M.; Vinas, L.; Vitali, B.; Vogel, G.; Wagner, R.; Wagner, R.; Wands, R.; Wang, Y.; Wang, C.; Wang, M.; Wardlaw, I.; Warren, M.; Werkema, S.; White Jr, H. B.; Whitmore, J.; Wielgos, R.; Wildberger, R.; Wills, L.; Winter, P.; Woods, R.; Worel, C.; Wu, Y.; Xia, L.; You, Z.; Yucel, M.; Zadeh, P.; Zanetti, A. M.; Zhadan, D.; Zhu, R.-Y.; Zifko, R.; Zutshi, V.

Abstract

The Mu2e experiment at Fermilab will search for the neutrinoless μ − → e − conversion in
the field of an aluminum nucleus. The Mu2e data-taking plan assumes two running periods, Run I
and Run II, separated by an approximately two-year-long shutdown. This paper presents an estimate
of the expected Mu2e Run I search sensitivity and includes a detailed discussion of the background
sources, uncertainties of their prediction, analysis procedures, and the optimization of the experimental
sensitivity. The expected Run I 5σ discovery sensitivity is R μe = 1.2 × 10 − 15 , with a total expected
background of 0.11 ± 0.03 events. In the absence of a signal, the expected upper limit is R μe < 6.2 × 10 − 16
at 90% CL. This represents a three order of magnitude improvement over the current experimental limit
of R μe < 7 × 10 − 13 at 90% CL set by the SINDRUM II experiment.

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Permalink: https://www.hzdr.de/publications/Publ-35975


Investigation of the ¹⁴N(p,γ)¹⁵O reaction and its impact on the CNO cycle

Frentz, B.; Aprahamian, A.; Boeltzig, A.; Borgwardt, T.; Clark, A. M.; Deboer, R. J.; Gilardy, G.; Görres, J.; Hanhardt, M.; Henderson, S. L.; Howard, K. B.; Kadlecek, T.; Liu, Q.; Macon, K. T.; Moylan, S.; Reingold, C. S.; Robertson, D.; Seymour, C.; Strauss, S. Y.; Strieder, F.; Vande Kolk, B.; Wiescher, M.

Abstract

The CNO cycle is the main energy source in massive stars during their hydrogen burning phase, and, for our
sun, it contributes at the ≈1% level. As the ¹⁴N(p,γ)¹⁵O reaction is the slowest in the cycle, it determines the
CNO energy production rate and thus the CNO contribution to the solar neutrino flux. These CNO neutrinos are
produced primarily from the β decay of ¹⁵O and, to a lesser extent, from the decay of ¹³N. Solar CNO neutrinos
are challenging to detect, but they can provide independent new information on the metallicity of the solar core.
Recently, CNO neutrinos from ¹⁵O have been identified for the first time with the Borexino neutrino detector
at the INFN Gran Sasso underground laboratory. There are, however, still some considerable uncertainties in
the ¹⁴N(p,γ)¹⁵O reaction rate under solar temperature conditions. The low energy reaction data presented
here, measured at the CASPAR underground accelerator, aim at connecting existing measurements at higher
energies and attempts to shed light on the discrepancies between the various data sets, while moving towards a
better understanding of the ¹⁴N(p,γ)¹⁵O reaction cross section. The present measurements span proton energies
between 0.27 and 1.07 MeV, closing a critical gap in the existing data. A multichannel R-matrix analysis was
performed with the entire new and existing data sets and is used to extrapolate the astrophysical S factors of the
ground state and the 6.79 MeV transition to low energies. The extrapolations are found to be in agreement with
previous work, but find that the discrepancies between measured data and R-matrix fits, both past and present,
still exist. We examine the possible reasons for these discrepancies and thereby provide recommendations for
future studies.

Permalink: https://www.hzdr.de/publications/Publ-35974


Low-energy Cross Section Measurements of ¹²C(p,γ) Deep Underground at LUNA

Skowronski, J.; Boeltzig, A.

Abstract

The ¹²C(p,γ)¹³N reaction cross section is currently under investigation in the low-background environment of the Laboratory for Underground Nuclear Astrophysics (LUNA). It is being studied using different types of solid targets, and employing two complementary detection techniques: HPGe spectroscopy and activation counting. To reduce systematic uncertainties, targets have been accurately characterized and their degradation under the intense beam of the LUNA-400 accelerator monitored. We present the experimental techniques and the corresponding analyses used to extract the reaction cross section.

  • Open Access Logo Contribution to proceedings
    Nuclear Physics in Astrophysics - X, 04.-09.09.2022, CERN, Switzerland
    EPJ Web of Conferences: EDP Sciences, 2100-014X, 03002
    DOI: 10.1051/epjconf/202327903002

Permalink: https://www.hzdr.de/publications/Publ-35973


Thermal neutron background at Laboratorio Subterráneo de Canfranc (LSC)

Plaza, J.; Martínez, T.; Bécares, V.; Cano-Ott, D.; Villamarín, D.; Pérez De Rada, A.; Mendoza, E.; Pesudo, V.; Santorelli, R.; Peña, C.; Balibrea-Correa, J.; Boeltzig, A.

Abstract

The thermal neutron background at Laboratorio Subterráneo de Canfranc (LSC) has been determined using several ³He proportional counter detectors. Bare and Cd shielded counters were used in a series of long measurements. Pulse shape discrimination techniques were applied to discriminate between neutron and gamma signals as well as other intrinsic contributions. Montecarlo simulations allowed us to estimate the sensitivity of the detectors and calculate values for the background flux of thermal neutrons inside Hall-A of LSC. The obtained value is (3.5±0.8)×10⁻⁶ n/cm²s, and is within an order of magnitude compared to similar facilities.

Keywords: Underground neutron background; Thermal neutron flux; ³He proportional counter; Pulse shape discrimination

Permalink: https://www.hzdr.de/publications/Publ-35972


Exploring Stars in Underground Laboratories: Challenges and Solutions

Aliotta, M.; Boeltzig, A.; Depalo, R.; Gyürky, G.

Abstract

For millennia, mankind has been fascinated by the marvel of the starry night sky. Yet, a proper scientific understanding of how stars form, shine, and die is a relatively recent achievement, made possible by the interplay of different disciplines as well as by significant technological, theoretical, and observational progress. We now know that stars are sustained by nuclear fusion reactions and are the furnaces where all chemical elements continue to be forged out of primordial hydrogen and helium. Studying these reactions in terrestrial laboratories presents serious challenges and often requires developing ingenious instrumentation and detection techniques. Here, we reveal how some of the major breakthroughs in our quest to unveil the inner workings of stars have come from the most unexpected of places: deep underground. As we celebrate 30 years of activity at the first underground laboratory for nuclear astrophysics, LUNA, we review some of the key milestones and anticipate future opportunities for further advances both at LUNA and at other underground laboratories worldwide.

Keywords: stellar evolution; nucleosynthesis; nuclear astrophysics experiments; background suppression underground

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Permalink: https://www.hzdr.de/publications/Publ-35971


Data publication: Towards High-Repetition Rate Petawatt Laser Experiments with Cryogenic Jets Using a Mechanical Chopper System

Rehwald, M.; Assenbaum, S.; Bernert, C.; Curry, C. B.; Gauthier, M.; Glenzer, S. H.; Göde, S.; Schoenwaelder, C.; Treffert, F.; Schramm, U.; Zeil, K.

Abstract

Rohdaten und Ausgewertete Messungen, die in der Publikation dargestellt sind.

Involved research facilities

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-35970


PIConGPU: Scaling high-fidelity plasma simulations up to exascale compute systems and a view on recent applications

Debus, A.; Steiniger, K.; Bastrakov, S.; Bastrakova, K.; Bussmann, M.; Carstens, F.-O.; Chandrasekaran, S.; Garten, M.; Gruber, B. M.; Hernandez Arreguin, B.; Hübl, A.; Juckeland, G.; Kelling, J.; Lebedev, A.; Leinhauser, M.; Marre, B. E.; Meyer, F.; Ordyna, P.; Pausch, R.; Pöschel, F.; Rogers, D.; Schramm, U.; Sprenger, L.; Starke, S.; Thévenet, M.; Trojok, J.; Wang, M.; Widera, R.; Young, J.

Abstract

PIConGPU’s latest release 0.6.0 in December 2021 brought a number of new features. Among these are an arbitrary-order Maxwell solver, the Higuera-Cary pusher, collisions, and incident field generation via the total field/scattered field technique enhancing its numerical stability and predictive capabilities.
Furthermore, there are various technical advances, most notably support of the HIP computational backend allowing to run on AMD GPUs. These advances are mainly driven by our participation in OLCF’s Frontier Center for Accelerated Application Readiness providing access to the hardware platform of the Frontier exascale supercomputer scheduled for deployment later this year. We show performance data and present recent applications of PIConGPU profiting from these developments. To these applications belongs the advanced laser-plasma accelerator scheme Traveling-wave electron acceleration (TWEAC), providing scalability to energies beyond 10 GeV while avoiding staging. We further present simulation campaigns modeling and delivering valuable insight into the micrometer and femtosecond plasma dynamics of existing experimental campaigns.

Keywords: PIConGPU; particle-in-cell code; TWEAC; Laser-plasma accelerator

  • Poster
    8. Annual MT meeting, 26.-27.9.2022, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35969


Towards High-Repetition Rate Petawatt Laser Experiments with Cryogenic Jets Using a Mechanical Chopper System

Rehwald, M.; Assenbaum, S.; Bernert, C.; Curry, C. B.; Gauthier, M.; Glenzer, S. H.; Göde, S.; Schoenwaelder, C.; Treffert, F.; Schramm, U.; Zeil, K.

Abstract

Laser-plasma based ion accelerators require suitable high-repetition rate target systems that enable systematic studies at controlled plasma conditions and application-relevant particle flux. Self-refreshing, micrometer-sized cryogenic jets have proven to be an ideal target platform. Yet, operation of such systems in the harsh environmental conditions of high power laser induced plasma experiments have turned out to be challenging. Here we report on recent experiments deploying a cryogenic hydrogen jet as a source of pure proton beams generated with the PW-class ultrashort pulse laser DRACO. Damage to the jet target system during application of full energy laser shots was prevented by implementation of a mechanical chopper system interrupting the direct line of sight between the laser plasma interaction zone and the jet source.

Involved research facilities

Related publications

  • Open Access Logo Contribution to proceedings
    13th Int. Particle Acc. Conf. IPAC2022, 12.-17.06.2022, Bangkok, Thailand
    Proceedings of the 13th International Particle Accelerator Conference, Geneva, Switzerland: JACoW Publishing, 978-3-95450-227-1
    DOI: 10.18429/JACoW-IPAC2022-WEIXSP1

Permalink: https://www.hzdr.de/publications/Publ-35968


Supporting Data for PhD Dissertation of Klara Lünser, TU Dresden, 2022

Lünser, K.

Abstract

This collection belongs to the PhD Dissertation of Klara Lünser with the title "Martensitische Phasenumwandlungen und Zwillingsbildung in epitaktisch gewachsenen Nickel-Titan-Schichten" (Martensitic phase transitions and twinning in epitaxial nickel-titanium thin films). The folder contains raw data of atomic force microscopy, resistivity, in situ scanning electron and pole figure measurements. It also contains the MATLAB code used for calculations of pole figures and inverse pole figures with martensite theories. The file "Probenzuordnung" explains which sample and data was used for which figure in the dissertation. 

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Permalink: https://www.hzdr.de/publications/Publ-35967


Self-evaluation Photon and Neutron RIs for FAIR data certification

Lambert, S.; McBirnie, A.; Matthews, B.; Fiedler, M.; Gagey, B.; Görzig, H.; Knodel, O.; Kourousias, G.; Markvardsen, A.; Minotti, C.; Ounsy, M.; Schön, S.; Soler, N.; Spruce, D.; Vukolov, A.; Collins, S.; Pozsa, K.

Abstract

This ExPaNDS project deliverable describes a FAIR self-assessment undertaken by the ten
ExPaNDS partner Photon and Neutron Research Infrastructures (PaN RIs) over the
three-month period July – September 2022. After reviewing selected examples of existing
FAIR evaluation frameworks designed to enable assessment at different levels (dataset,
repository, and organisation), the report describes the evaluation approach adopted for the
ExPaNDS FAIR self-assessment. As no existing framework met our specific need to focus
on FAIR workflows and processes in PaN RIs, it was necessary to select, combine, and
adapt existing frameworks. Supported by four underlying guiding principles, our approach
drew heavily on the FAIR Principles, the RDA FAIR Data Maturity Model, and FAIRsFAIR’s
CoreTrustSeal+FAIRenabling framework. Post-evaluation feedback from ExPaNDS partners
indicated that they found the FAIR self-assessment a useful and valuable exercise for
understanding current levels of FAIRness at their facilities and for articulating what
implementations they have in progress or planned to support FAIR in future. A key output of
the ExPaNDS FAIR evaluation is the collected self-assessment reports from the ten partner
facilities. These reports are published openly and in full as part of the deliverable. In addition,
the self-assessments are supplemented with some high-level observations on the state of
the FAIR journey across the ExPaNDS facilities.

Keywords: FAIR; Metadata; ExPaNDS; European Photon and Neutron facilities

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Permalink: https://www.hzdr.de/publications/Publ-35966


Traveling-wave electron accelerators – leveraging exascale computing towards scalable laser-plasma accelerators

Debus, A.; Steiniger, K.; Widera, R.; Bastrakov, S.; Carstens, F.-O.; Meyer, F.; Pausch, R.; Lebedev, A.; Garten, M.; Kluge, T.; Kelling, J.; Hernandez Arreguin, B.; Young, J.; Pöschel, F.; Hübl, A.; Rogers, D.; Juckeland, G.; Chandrasekaran, S.; Bussmann, M.; Schramm, U.

Abstract

Traveling-wave electron acceleration (TWEAC) is an advanced laser-plasma accelerator scheme, which is neither limited by dephasing, nor by pump depletion or diffraction. Such accelerators are scalable to energies beyond 10 GeV without the need for staging and are candidates for future compact electron-positron colliders based on existing CPA lasers.
Requiring to model a large plasma volume in 3D at high-resolution over an extended acceleration distance for high-fidelity results, TWEAC simulations need exascale compute resources -- even "small" test simulations need hundreds of GPUs.
We present recent progress in TWEAC simulations and various technical advances in the 3D3V particle-in-cell code PIConGPU that enable running on the upcoming Frontier cluster (#1 in TOP500), most notably support of the HIP computational backend allowing to run on AMD GPUs, as well as openPMD, PICMI and algorithmic developments. These advances are mainly driven by our participation in OLCF’s Frontier Center for Accelerated Application Readiness providing access to the hardware platform of the Frontier exascale supercomputer. We show performance data and present recent applications of PIConGPU profiting from these developments.

Keywords: TWEAC; Traveling-wave electron accelerators; laser pulse-front tilt; Laser-plasma accelerator; PIConGPU; particle-in-cell code

  • Poster
    EuroNNAc Special Topic Workshop 2022, 18.-24.09.2022, Isola d'Elba, Italien

Permalink: https://www.hzdr.de/publications/Publ-35965


Ultrafast melting of Warm Dense Cu studied by x-ray spectroscopy

Smid, M.; Köhler, A.; Bowers, B.; Chang, Y.-Y.; Couperus Cabadağ, J. P.; Huang, L.; Kozlová, M.; Kurz, T.; La Berge, M.; Pan, X.; Perez-Martin, P.; Ruiz De Los Panos, I. L.; Schöbel, S.; Vorberger, J.; Zarini, O.; Cowan, T.; Schramm, U.; Irman, A.; Falk, K.

Abstract

We present novel experimental results of ultra fast heating of Warm Dense Cu diagnosed by means of x-ray absorption and emission spectroscopy carried out at the Draco laser facility at HZDR in 2021. A thin Cu foil was directly heated to few eV temperature by an ultra short laser pulse (40 fs, 2e15 W/cm2) and probed with variable delay in the range 0.2-20 ps by a laser-driven betatron radiation. This betatron radiation, created by a laser wakefield accelerator, is an unique x-ray source with its ultra short duration and broadband spectrum, therefore ideally suited for studies of non-equilibrium dense plasmas while its high brightness allows for single-shot measurement. The sample is studied via the X-ray absorption spectroscopy in the region above the Cu K-edge. This method provides temporally-resolved information about both the ionic structure of the matter and its temperature during the process of ultrafast heating and melting of the material. The measured spectra are understood and analyzed by using Ab initio simulations and the temporal evoution of heatig and melting is compared to PIC simulations to infer the electron to ion energy transer.

Involved research facilities

  • Draco
  • Lecture (Conference)
    64th Annual Meeting of the APS Division of Plasma Physics, 17.-21.10.2022, Spokane, United States of America

Permalink: https://www.hzdr.de/publications/Publ-35964


High-fidelity particle-in-cell simulations at multiple scales

Debus, A.

Abstract

The particle-in-cell method is central to providing a kinetic description of the relativstic, nonlinear plasma dynamics -- particularly when interacting with ultrashort laser pulses and particle beams. Its broad applicability ranges from advanced plasma accelerators of electrons or ions, warm dense matter to astrophysics. A major challenge to a better understanding is to integrate disparate spatial and temporal scales, as well as physics into consistent, predictive models that can be compared to experimental results. While the large-scale dynamics is often determined by hydrodynamic evolution, the microscale physics includes ionization, radiation processes from infrared to xrays, atomic physics, as well as QED effects. Interfacing and integrating domain-specific numerical codes, such as particle trackers, FEL codes, requires data standards for seamless data exchange. Based on recent examples from plasma accelerator research using the 3D3V particle-in-cell code PIConGPU, I will outline the state-of-the art and challenges of particle-in-cell simulations to and show current strategies of solving them in large-scale simulations on heterogenous high-performance computing environments.

Keywords: Particle-in-cell; PIConGPU; multi-scale

  • Invited lecture (Conferences)
    Multiscale Modeling of Matter under Extreme Conditions, 11.-16.09.2022, Görlitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35963


Chelator-based non-peptidic radiotracers for PET imaging of PD-L1 with copper-64

Krutzek, F.; Donat, C.; Ullrich, M.; Loureiro, L. R.; Kopka, K.; Stadlbauer, S.

Abstract

Objective: The programmed cell death-ligand 1 (PD-L1) is upregulated on many different cancers and allows the tumor cells to evade immune response through binding to the PD-1 receptor.[1] Monoclonal antibodies, i.e. checkpoint inhibitors, are able to break this blockade and thus reactivate the immune system.[2] However, only 30% of the patients respond to antibody-based immunotherapy. Because PD-L1 is heterogeneously expressed within and across tumor sites, there is an urgent clinical need for a non-invasive, diagnostic imaging approach helping for therapy decision. Radiotracers for PET and SPECT imaging are able to meet these requirements. Especially small molecules are favourable, because of their short clearance times and for providing high imaging contrast.[3]

Methods: Modification of two literature known small molecule PD-L1 inhibitors with water-solubilizing groups, different linkers and a DOTA chelator resulted in six different radioligands. Labeling was performed with Cu-64 (HZDR, 30 MeV TR-FLEX cyclotron) and binding affinities to PD-L1 were determined in vitro on transduced PC3 cells stably overexpressing human PD-L1. Qualitative PET scans (nanoSCAN PET/CT scanner, Mediso) were performed in NMRI-FoxN1-nude mice bearing PC3-hPD-L1 xenografted tumors.

Results: Organic synthesis started from biaryl building blocks (R1 = H, R2 = Br and R1 = R2 = Me), which underwent a Mitsunobu reaction with the central chloroaryl moiety. The bis(sulfonic acid) group was attached via a sarcosine spacer. Three different linker structures were synthesized and attached by Cu(I)-catalyzed click reaction. Synthesis was finished with DOTA conjugation and subsequent quantitative labeling with Cu-64 under standard labeling conditions was achieved. Using the shake flask method, log(D) values ranging from –1.5 to –2.5 were obtained. Saturation binding assays revealed that biphenyl compounds with R1 = R2 = Me showed promising binding affinities to PD-L1 (KD between 60 and 123 nM). In micro-PET experiments, the radioligands exhibited unusual high circulation times. PET images obtained after 15 h p.i. showed the highest tumor uptake and moderate uptake in the liver.
Conclusion: A library of new PD-L1 targeting non-peptide radiotracers based on small molecule lead structures bearing water-soluble groups and a chelator was successfully synthesized. All compounds showed moderate binding affinities toward PD-L1. Qualitative PET/CT scans showed a moderate uptake in PD-L1 positive tumors. For improved pharmacokinetics the lipophilicity should be further reduced and DOTA replaced by more optimal chelators such as NODAGA to avoid possible copper transchelation in the liver.

References:

[1] M. A. Postow, M. K. Callahan, J. D. Wolchok, J Clin Oncol 2015, 33, 1974-1982.
[2] S. L. Topalian, C. G. Drake, D. M. Pardoll, Cancer cell 2015, 27, 450-461.
[3] S. Chatterjee, W. G. Lesniak, S. Nimmagadda, Mol. Imaging 2017, 16, 1-5.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    International Symposium on Radiopharmaceutical Sciences, 29.05.-02.06.2022, Nantes, France

Permalink: https://www.hzdr.de/publications/Publ-35962


Traveling-wave electron accelerators – towards scalable laser-plasma accelerators beyond 10GeV

Debus, A.; Steiniger, K.; Widera, R.; Bastrakov, S.; Carstens, F.-O.; Meyer, F.; Pausch, R.; Garten, M.; Kluge, T.; Kelling, J.; Hernandez Arreguin, B.; Young, J.; Pöschel, F.; Hübl, A.; Rogers, D.; Juckeland, G.; Chandrasekaran, S.; Bussmann, M.; Schramm, U.

Abstract

Traveling-wave electron acceleration (TWEAC) is an advanced laser-plasma accelerator scheme, which is neither limited by dephasing, nor by pump depletion or diffraction. Such accelerators are scalable to energies beyond 10 GeV without the need for staging and are candidates for future compact electron-positron colliders based on existing CPA lasers. TWEAC utilizes two pulse-front tilted laser pulses whose propagation directions enclose a configurable angle. The accelerating cavity is created along their overlap region in the plasma and can move at the vacuum speed of light. The oblique laser geometry enables to constantly cycle different laser beam sections through the interaction region, hence providing quasi-stationary conditions of the wakefield driver.

The TWEAC geometry enables to access to a wide range of regimes, which are customizable in cavity geometry, laser-to-electron energy efficiency and the required laser properties at different plasma densities, making the scheme suitable for high-rep rate lasers at low energies per pulse to multi-PW laser facilities. Exploring these regimes in high-fidelity simulations is computationally highly demanding, as these need to include large plasma volumes in 3D at high-resolution over an extended acceleration distance. Since even "small" test simulations need hundreds of GPUs, TWEAC simulations require exascale compute resources.

We present recent progress in TWEAC simulations and various technical advances in the 3D3V particle-in-cell code PIConGPU that enable running on the upcoming Frontier cluster, most notably support of the HIP computational backend allowing to run on AMD GPUs, as well as openPMD, PICMI and algorithmic developments. These advances are mainly driven by our participation in OLCF’s Frontier Center for Accelerated Application Readiness providing access to the hardware platform of the Frontier exascale supercomputer. We show performance data and recent applications of PIConGPU profiting from these developments.

Keywords: Traveling-wave electron acceleration; TWEAC; PIConGPU; Laser-plasma accelerator; Particle-in-cell simulations

  • Lecture (Conference)
    Advanced Accelerator Concepts Workshop 2022, 06.-11.11.2022, Long Island, New York, USA

Permalink: https://www.hzdr.de/publications/Publ-35961


PIConGPU + X – Building blocks for successful Exascale accelerator simulations

Debus, A.; Steiniger, K.; Widera, R.; Bastrakov, S.; Carstens, F.-O.; Meyer, F.; Pausch, R.; Garten, M.; Bernert, C.; Kluge, T.; Willmann, A.; Kelling, J.; Hernandez Arreguin, B.; Young, J.; Pöschel, F.; Hübl, A.; Rogers, D.; Juckeland, G.; Hoffmann, N.; Chandrasekaran, S.; Schramm, U.; Bussmann, M.

Abstract

Exascale computing is close to becoming a reality. As technology progresses, it has become clear that heterogeneous computing is going to stay and adapting to new hardware is an ongoing challenge. Since 2015 PIConGPU has paved the way to accelerating plasma simulations across compute platforms using the Alpaka framework. This has enabled early adaption to new compute hardware and readiness for Exascale compute capabilities.
However, experience has shown that the real challenges are of a different nature. The first is in detailed analysis of the data produced in simulations. Here, we present our current work on I/O, code coupling, visual analytics and large-scale data analytics.
The second, and more pressing challenge, is comparison to experiment. Here, not only has the increasing quality of experiments put more demand on simulation quality, but more and more the demand for fast, close to real time analysis has grown. This puts high quality simulations to the test, as runs on supercomputers tend to be costly. We present workflows to match experiment and simulations and a future look on how feedback loops between experiment and simulation can be optimized.

Keywords: Particle-in-cell; PIConGPU; exascale; performance portable; synthetic diagnostics

  • Invited lecture (Conferences)
    Advanced Accelerator Concepts Workshop 2022, 06.-11.11.2022, Hyatt Regency, Hauppauge, Long Island, NY, USA

Permalink: https://www.hzdr.de/publications/Publ-35960


Sub-band gap infrared absorption in Si implanted with Mg

Wang, M.; Shaikh, M. S.; Kentsch, U.; Heller, R.; Zhou, S.

Abstract

Single-crystalline Mg-implanted Si layers are synthesized by ion implantation followed by pulsed laser melting. The Mg doping concentration is reaching 10²¹ cm⁻³. The Raman, Rutherford backscattering spectrometry/channeling and particle induced x-ray emission measurements confirm the recrystallization of the Mg-implanted Si layer. A strong below band gap infrared absorption over the wavelength range of 1.4–6.2 µm (0.2–0.87 eV, in the mid-infrared range) has been observed in the Mg-implanted Si layers. It is associated with deep levels induced by Mg atoms at high implantation level. This work points out the potential of Mg-implanted Si for room-temperature light detection in a broad infrared range for the new generation of Si-based photonics.

Keywords: sub-band gap absorption; ion implantation; infrared photoresponse; deep-level impurity; Mg-implanted

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-35959


Learning Electron Bunch Distribution along a FEL Beamline by Normalising Flows

Willmann, A.; Couperus Cabadağ, J. P.; Chang, Y.-Y.; Pausch, R.; Ghaith, A.; Debus, A.; Irman, A.; Bussmann, M.; Schramm, U.; Hoffmann, N.

Abstract

Understanding and control of Laser-driven Free Electron Lasers remain to be difficult problems that require highly intensive experimental and theoretical research. The gap between simulated and experimentally collected data might complicate studies and interpretation of obtained results. In this work we developed a deep learning based surrogate that could help to fill in this gap. We introduce a surrogate model based on normalising flows for conditional phase-space representation of electron clouds in a FEL beamline. Achieved results let us discuss further benefits and limitations in exploitability of the models to gain deeper understanding of fundamental processes within a beamline.

  • Poster
    Machine Learning and the Physical Sciences, 03.12.2022, the New Orleans Convention Center in New Orleans, USA
  • Open Access Logo Contribution to proceedings
    Machine Learning and the Physical Sciences workshop, 03.12.2022, New Orleans, USA

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Permalink: https://www.hzdr.de/publications/Publ-35958


Spectroscopy of XFEL heated Cu and x-ray absorption in laser-produced Warm Dense Cu

Smid, M.

Abstract

We report on a recent (Feb 2022) experiment on the spectroscopic characterization of XFEL-heated Cu foil targets. The 1-5μm thick Cu foils were irradiated by the tightly focused XFEL beam (~1μm focus, up till 1mJ in energy, European XFEL), heating the target to more then 100 eV, and clearly observing emission from ions up till Cu 25+. Three crystal spectrometers were measuring the emission and scattering in the range ~ 8000 - 9800 eV, i.e. covering the lines of Cu Kα and Kβ, including their ionized satellites. The XFEL photon energy was varied in the range 8.8-9.8 keV. The primary aim is to resolve the continuum lowering by checking the shifts of K edge for various ionizations, in a similar manner as was done earlier on lighter elements. Apart from this, many interesting phenomena can be studied from this extensive dataset, like the double-core hole (hollow ion) emission and its shift, resnonances, XRTS, and even Xanes absorption, by comparing the emission from the front and rear sides of the target. Having those data available in a well characterized system provides a high demand as well as benchmark for precise atomic simulations, and in general leads to a better understanding of Warm Dense Copper on the atomic physics level.

Involved research facilities

  • Draco
  • Lecture (Conference)
    Radiative Properties of Hot Dense Matter, 14.-18.11.2022, Santa Fe, United States of America

Permalink: https://www.hzdr.de/publications/Publ-35957


Combined Au/Ag nanoparticle creation in ZnO nanopillars by ion implantation for optical response modulation and photocatalysis

Macková, A.; Jagerová, A.; Lalik, O.; Mikšová, R.; Poustka, D.; Mistrík, J.; Holý, V.; Schutter, J. D.; Kentsch, U.; Marvan, P.; Azarov, A.; Galeckas, A.

Abstract

ZnO nanopillars were implanted with Au-400 keV and Ag-252 keV ions with ion fluences from 1 × 10¹⁵ cm⁻² to 1 × 10¹⁶ cm⁻². We compared ZnO nanopillars solely implanted with Au-ions and dually-implanted with Au and Ag-ions. Rutherford Back-Scattering spectrometry (RBS) confirmed Ag and Au embedded in ZnO nanopillar layers in a reasonable agreement with theoretical calculations. A decreasing thickness of the ZnO nanopillar layer was evidenced with the increasing ion implantation fluences. Spectroscopic Ellipsometry (SE) showed a decrease of refractive index in the nanopillar parts with embedded Au, Ag-ions. XRD discovered vertical domain size decreasing with the proceeding radiation damage accumulated in ZnO nanopillars which effect was preferably ascribed to Au-ions. SE and diffuse reflectance spectroscopy (DRS) showed optical activity of the created nanoparticles at wavelength range 500 – 600 nm and 430 – 700 nm for the Au-implanted and Au, Ag-implanted ZnO nanopillars, respectively. Photoluminescence (PL) features linked to ZnO deep level emission appear substantially enhanced due to plasmonic interaction with metal nanoparticles created by Ag, Au-implantation. Photocatalytic activity seems to be more influenced by the nanoparticles presented in the layer rather than the surface morphology. Dual implantation with Ag, Au-ions enhanced optical activity to a larger extent without significant morphology deterioration as compared to the solely Au-ion implanted nanopillars.

Keywords: ZnO nanopillars; Au/Ag nanoparticles; ion implantation; SPR; doped ZnO nanostructures

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Permalink: https://www.hzdr.de/publications/Publ-35956


Data publication: Energy relaxation and electron-phonon coupling in laser-excited metals

Zhang, J.; Qin, R.; Zhu, W.; Vorberger, J.

Abstract

DFT data and results for Al and Cu for the DOS, phonon DOS, and Eliashberg function depending on the electron temperature.

Keywords: electron-phonon; DFT; laser; laser-matter interaction; two-temperature model; relaxation; energy transfer

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Permalink: https://www.hzdr.de/publications/Publ-35955


Nonlinear dynamics of Dirac fermions in topological HgTe structures

Uaman Svetikova, T. A.; Pashkin, O.; de Oliveira, T.; Bayer, F.; Berger, C.; Fuerst, L.; Buhmann, H.; Molenkamp, L. W.; Helm, M.; Kiessling, T.; Winnerl, S.; Kovalev, S.; Astakhov, G.

Abstract

High harmonic generation (HHG) has applications in various fields, including ultrashort pulse measurements, material characterization and imaging microscopy. Strong THz nonlinearity and efficient third harmonic generation (THG) were demonstrated in graphene [1], therefore it is natural to assume the presence of the same effect in other Dirac materials, such as topological insulators (TI). Topological states can be found in HgTe quantum wells with a thickness of more than 6.3 nm [2], and strained 3D Hg1-xCdxTe thin films with cadmium fraction x < 0.16 [3].
We used a series of HgTe samples corresponding to three qualitatively different cases: 2D trivial and topological structures and 3D topological insulators. By using moderate THz fields, the presence of highly efficient THG was measured in these samples at different temperatures and THz powers. This provides insight into physical mechanisms leading to THG in TIs. For in-depth understanding of Dirac fermions dynamics and dominating scattering mechanisms in HgTe TI, we conducted THz pump-probe experiments that reveal several relaxation time scales.

[1] Hafez, H. A. et al., Nature 561, 507 (2018).
[2] Bernevig, B. et al. Science 314, 5806 (2006): 1757-1761.
[3] Brüne, C., et al. Phys. Rev. Lett. 106, 12 (2011): 126803.

Keywords: topological insulators; HgTe; nonlinear dynamics

Involved research facilities

  • F-ELBE
  • Lecture (Conference)
    3rd QMA retreat, 12.-14.10.2022, Friedrichroda, Deutschland
  • Poster
    DPG Meeting of the Condensed Matter Section (SKM): Regensburg 2022, 04.-09.09.2022, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35954


Nonlinear parameters of Dirac fermions in HgTe structures: trivial and topological

Uaman Svetikova, T. A.; Pashkin, O.; de Oliveira, T.; Bayer, F.; Berger, C.; Fuerst, L.; Buhmann, H.; Molenkamp, L. W.; Helm, M.; Kiessling, T.; Winnerl, S.; Kovalev, S.; Astakhov, G.

Abstract

High harmonic generation (HHG) has applications in various fields, including ultrashort pulse measurements, material characterization and imaging microscopy. Strong THz nonlinearity and efficient third harmonic generation (THG) were demonstrated in graphene [1], therefore it is natural to assume the presence of the same effect in other Dirac materials, such as topological insulators (TI) [2,3]. Topological states can be found in HgTe quantum wells with a thickness of more than 6.3 nm [4], and strained 3D Hg1-xCdxTe thin films with cadmium fraction x < 0.16 [5]. We used a series of HgTe samples corresponding to three qualitatively different cases: 2D trivial and topological structures and 3D topological insulators. By using moderate THz fields, the presence of highly efficient THG was measured in these samples at different temperatures and THz powers. This provides insight into physical mechanisms leading to THG in TIs. For in-depth understanding of Dirac fermions dynamics and dominating scattering mechanisms in HgTe TI, we
conducted THz pump-probe experiments that reveal several relaxation time scales.

[1] Hafez, H. A. et al., Nature 561, 507 (2018).
[2] Kovalev, S. et al. Quantum Materials 6.1 (2021): 1-6.
[3] Giorgianni, F. et al. Nature Сommunications 7.1 (2016): 1-6.
[4] Bernevig, B. et al. Science 314, 5806 (2006): 1757-1761.
[5] Brüne, C. et al. Phys. Rev. Lett. 106, 12 (2011): 126803.

  • Poster
    International conference on Complexity and Topology in Quantum Matter, 25.-29.07.2022, Würzburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35953


Data publication: Characterization of laser wakefield acceleration efficiency with octave spanning near-IR spectrum measurements

Streeter, M. J. V.; Ma, Y.; Kettle, B.; Dann, S. J. D.; Gerstmayr, E.; Albert, F.; Bourgeois, N.; Cipiccia, S.; Cole, J. M.; Gallardo González, I.; Hussein, A. E.; Jaroszynski, D. A.; Falk, K.; Krushelnick, K.; Lemos, N.; Lopes, N. C.; Lumsdon, C.; Lundh, O.; Mangles, S. P. D.; Najmudin, Z.; Rajeev, P. P.; Sandberg, R.; Shahzad, M.; Smid, M.; Spesyvtsev, R.; Symes, D. R.; Vieux, G.; Thomas, A. G. R.

Abstract

10.5281/zenodo.7188057

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  • Reseach data in external data repository
    Publication year 2022
    License: Creative Commons Attribution 4.0 International
    Hosted on https://zenodo.org/record/7188057: Link to location
    DOI: 10.5281/zenodo.7188057

Permalink: https://www.hzdr.de/publications/Publ-35952


Characterization of laser wakefield acceleration efficiency with octave spanning near-IR spectrum measurements

Streeter, M. J. V.; Ma, Y.; Kettle, B.; Dann, S. J. D.; Gerstmayr, E.; Albert, F.; Bourgeois, N.; Cipiccia, S.; Cole, J. M.; Gallardo González, I.; Hussein, A. E.; Jaroszynski, D. A.; Falk, K.; Krushelnick, K.; Lemos, N.; Lopes, N. C.; Lumsdon, C.; Lundh, O.; Mangles, S. P. D.; Najmudin, Z.; Rajeev, P. P.; Sandberg, R.; Shahzad, M.; Smid, M.; Spesyvtsev, R.; Symes, D. R.; Vieux, G.; Thomas, A. G. R.

Abstract

We report on experimental measurements of energy transfer efficiencies in a GeV-class laser wakefield accelerator. Both the transfer of energy from the laser to the plasma wakefield and from the plasma to the accelerated electron beam was diagnosed by simultaneous measurement of the deceleration of laser photons and the acceleration of electrons as a function of plasma length. The extraction efficiency, which we define as the ratio of the energy gained by the electron beam to the energy lost by the self-guided laser mode, was maximized at 19±3% by tuning the plasma density and length. The additional information provided by the octave-spanning laser spectrum measurement allows for independent optimization of the plasma efficiency terms, which is required for the key goal of improving the overall efficiency of laser wakefield accelerators.

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Permalink: https://www.hzdr.de/publications/Publ-35951


Deterministic multi-level spin orbit torque switching using focused He+ ion beam irradiation

Kurian, J.; Joseph, A.; Cherifi-Hertel, S.; Fowley, C.; Hlawacek, G.; Dunne, P.; Romeo, M.; Atcheson, G.; Coey, J. M. D.; Doudin, B.

Abstract

He+ ion irradiation is used to pattern multiple areas of Pt/Co/W films with different irradiation doses in Hall bars. The resulting perpendicular magnetic anisotropy landscape enables selective multilevel currentinduced switching, with full deterministic control of the position and order of the individual switching elements. Key pattern design parameters are specified, opening a way to scalable multilevel switching devices.

Keywords: spintronics; spin orbit torque switching; nanomagnetism; ion beam irradiation; Hall bars

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Permalink: https://www.hzdr.de/publications/Publ-35950


Material requirements and choices for non destructive pulsed magnets

Zherlitsyn, S.

Abstract

Es hat kein Abstrakt vorgelegen

Involved research facilities

  • High Magnetic Field Laboratory (HLD)
  • Invited lecture (Conferences)
    2022 MRS fall meeting & exhibit, 27.11.-02.12.2022, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-35949


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